Ekos is an advanced cross-platform (Windows®, Mac® OS, Linux®) observatory control and automation tool with a particular focus on Astrophotography. It is based on a modular extensible framework to perform common astrophotography tasks. This includes highly accurate GOTOs using astrometry solver, ability to measure and correct polar alignment errors, auto-focus & auto-guide capabilities, and capture of single or stack of images with filter wheel support. Ekos is shipped with KStars.

Ekos introductory video


  • Control your telescope, CCD (& DSLRs), filter wheel, focuser, guider, adaptive optics unit, and any INDI-compatible auxiliary device from Ekos.

  • Built-in native autoguiding with support for automatic dithering between exposures and support for Adaptive Optics devices in addition to traditional guiders.

  • Extremely accurate GOTOs using astrometry.net solver (both Online and Offline solvers supported).

  • Load & Slew: Load a FITS image, slew to solved coordinates, and center the mount on the exact image coordinates in order to get the same desired frame.

  • Measure & Correct Polar Alignment errors using astromety.net solver.

  • Easy to use Polar Alignment Assistant tool. A very quick and reliable tool to polar align your German Equatorial Mount!

  • Capture and record video streams in SER format.

  • Completely automated scheduler to control all your observatory equipment, select the best targets for imaging given current conditions and constraints, monitor weather conditions, and capture your data while you are away!

  • Smart Dark Library: All your dark frames with different binning/temperature/frame settings are saved for future use. Ekos re-uses dark frames intelligently without taking unnecessary captures. You can configure how long you want to reuse all the dark frames.

  • Define multiple driver profiles for local and remote setups. Switch among them easily.

  • Auto and manual focus modes using Half-Flux-Radius (HFR) method.

  • Automated unattended meridian flip. Ekos performs post meridian flip alignment, calibration, focusing, and guiding to resume the capture session.

  • Automatic focus between exposures when a user-configurable HFR limit is exceeded.

  • Powerful sequence queue for batch capture of images with optional prefixes, timestamps, filter wheel selection, and much more!

  • Export and import sequence queue sets as Ekos Sequence Queue (.esq) files.

  • Center the telescope anywhere in a captured FITS image or any FITS with World Coordinate System (WCS) header.

  • Automatic flat field capture, just set the desired ADU and let Ekos does the rest!

  • Automatic abort and resumption of exposure tasks if guiding errors exceed a user-configurable value.

  • Support for dome slaving.

  • Complete integration with KStars Observation Planner and SkyMap.

  • Fully scriptable via D-Bus.

  • Integrate with all INDI native devices.

Ekos Setup

Ekos Summary

Ekos is a part of KStars. KStars/Ekos is already included with your StellarMate gadget. It is also available for Linux®, Mac® OS, and Windows® if you want to install on your primary machine. After you run KStars on your PC or on StellarMate (Either directly via HDMI or via VNC), Ekos can be accessed from the Tools menu or via the Ekos on the main toolbar, or by a keyboard shortcut (Ctrl+K). In addition to the Ekos window, KStars provides a more detailed INDI Control Panel where you can directly set and control the device parameters.

When running Ekos, it is not necessary to start INDI Server via StellarMate Web Manager as Ekos manages that transparently.

KStars Main Window

User Interface

Ekos Astrophotography Tool is organized into several Modules. A module is a set of functions and tasks for a particular step in astrophotography and/or data acquisition. Currently, the following modules are included with Ekos:

  • Setup & Summary Module

  • Scheduler Module

  • Capture Module

  • Focus Module

  • Alignment Module

  • Guide Module

  • Mount Module

Each module has its own tab and icon in the graphical user interface as illustrated in the screenshot below:

Ekos summary cheatsheet
Summary & Setup Module

As its name suggests, this is where you will create and manage your equipment profile, and connect to your devices. It also provides a summary view where the capture progress along with the focus & guide operations is displayed in a compact format to convey the most important information relevant to the user.

Scheduler Module

After mastering Ekos, users are encouraged to learn how to use the Scheduler module since it facilitates the complete observation process greatly. It enables you to select multiple targets, specify which conditions and requirements to be met, and what frames are required for capture. Afterwards the scheduler intelligently calculates the best observation time for each object and then proceed to control the complete observatory from startup to shutdown.

Capture Module

This is the primary module for camera & filter wheel control. Create imaging sequences, capture previews, and watch video streams. It supports rotator control and can automatically capture flat frames in a number of scenarios.

Focus Module

Measure the sharpness of your images in the focus module by calculating Half-Flux-Radius. The lower the HFR, the sharper the image becomes. You can run the focus module with or without a focuser. With an electronic focuser, you can run an autofocus operation where Ekos iterates and calculates the optical focus position.

Guide Module

To achieve long exposure astrophotography, guiding is necessary to ensure the image is locked and stabilized for the complete duration of the exposure duration. Deviations from the frame with time can lead to blurry images and star trails. In the guide module, it can automatically select a suitable guide star and then lock the mount to always keep that star in its position. If the guide module detects any deviation from this locked position, it sends correction pulses to the mount to bring it back to the original position.

Mount Module

Mount control can be either done via the Sky Map interactively or via the Mount Control Panel in the mount module. Configure telescope properties (focal length & aperture) for both your primary imaging telescope and guide scope. However, it is recommended to select the telescopes in the equipment profile and not change the values directly in the mount module.

Profile Wizard

The Profile Wizard is a handy tool to setup your equipment for the first time. It should popup automatically the first time you run KStars. Follow the guided instructions to setup your first equipment profile.

Greeting Page
Profile Wizard Welcome

The first greeting screen contains some links to learn more about Ekos & INDI. Click Next to continue.

Equipment Location Page

Next, you will be presented with the equipment location page. Your selection depends on where your equipment is connected to:

  • Equipment is attached to this device: Select this option if Ekos is running on your StellarMate (via HDMI or VNC), device (Windows®/Linux®) or Mac® OS.

  • Equipment is attached to a remote device: Select this option if Ekos is running on your device (Windows®/Linux®) or Mac® OS, and your equipment is connected to a remote computer.

  • Equipment is attached to StellarMate: Select this option if Ekos is running on your device (Windows®/Linux®) or Mac® OS, and your equipment is connected to StellarMate.

Equipment location page

Click Next to continue.

Remote Connection Page

In case selected the 2nd option in the last step, you shall be presented with the Remote Connect Page, here you will enter the hostname or IP address of the StellarMate unit. You can get the hostname from the StellarMate mobile App. Alternatively, you can construct the hostname from StellarMate HotSpot SSID. You should see the SSID when you search for WiFi networks nearby. For example, suppose the SSID is stellarmate. The hostname should be stellarmate.local. That is, if you remove the underscore, and append .local, then you will get the unit hostname. You can always use the StellarMate App to change the unit default hostname to the name of your choice.

Profile Wizard Remote page

For the INDI Manager question, always select Yes since StellarMate Web Manager is running by default on the unit. Click Next to continue.

Profile Creation Page

Now you get to name your equipment profile. Afterwards select which guider application to use. The Internal Guider is the only officially supported selection in StellarMate. You may opt to select PHD2/LinGuider but the details are out of the scope of this documentation. If additional services are desired, check the ones you want to run.

The final page of Profile Wizard

In the example above, we select Remote Astrometry, WatchDog, and SkySafari drivers. The detailed explanations for each is provided in the tooltip when you over them. Once done, click Create Profile button. You should now be presented with the Profile Editor.

Profile Editor

Profile Editor

You can define profiles for your equipment and their connection mode using the Profile Editor. Ekos comes pre-installed with the Simulators profile which can be used to start simulator devices for demonstration purposes:

  • Connection Mode: Ekos can be started either locally or remotely. Local mode is when Ekos is running in the same machine as INDI server, i.e. all the devices are connected directly to the machine. If you run INDI server on a remote machine (for example, on a Raspberry PI), you need to set the INDI server host and port.

  • Auto Connect: Check this option to enable automatic connection to all your devices after INDI server is started. If unchecked, INDI devices are created but not automatically connected. This is useful when you want to make changes to the driver (e.g. change baud rate or IP address or any other settings) before you connect to it.

  • Site Info: Optionally, you can check the Site Info checkbox and Ekos will load the current city and timezone whenever is Ekos is started with this profile. This can be useful when connecting to the remote geographic site so that Ekos is in sync location and time wise.

  • Guiding: Select which Guide application you want to use for guiding. By default, the Ekos internal Guide Module is utilized. External guiders include PHD2 and LinGuider.

  • INDI Web Manager: StellarMate Web Manager is a web-based tool to start and stop INDI drivers. You should always check this option when connecting remotely to a StellarMate unit.

  • Device Selection: Select your devices from each category. Please note that if you have a CCD with a guide head, you can leave the guider drop-down menu blank as Ekos will auto-detect the guide head from the CCD camera. Similarly, if your CCD includes embedded filter wheel support, then you do not need to specify the filter wheel device in the filter drop-down menu.

Start & Stop INDI

Start and Stop INDI services. Once INDI server is established, INDI Control Panel will be displayed. Here you can change some driver options such as which port the device is connected to etc.

Connect & Disconnect Devices

Connect to INDI server. Based on the devices connected, Ekos modules (CCD, Focus, Guide, etc.) will be established and available to use.

Once you are ready, click Start INDI to establish INDI server and connection to your equipment. Ekos shall create the various module icons (Mount, Capture, Focus, etc.) as the connection is established with the device.


Logging is a very important tool in order to diagnose any issues with either INDI drivers or Ekos. Before submitting any support request, the log must be attached in order to help diagnose the exact issue. Depending on the exact problem, you may need to enable logging for the feature or drivers that exhibit issues. Enabling logging for everything is not recommended as it will produce too much data that would be useful to diagnose the issue and could result in missing the root cause all other. So only enable the necessary logs.

The following short video explains how to use the Logging feature to submit logs.

Logging feature


Ekos Capture

The CCD Module is your primary image and video acquisition module in Ekos. It enables you to capture single (Preview), multiple images (Sequence Queue), or record SER videos along with a selection of filter wheel and rotator, if available.

CCD & Filter Wheel Group

Select the desired CCD/DSLR and Filter Wheel (if available) for capture. Set CCD temperature and filter settings.

  • CCD: Select the active CCD camera. If your camera has a guide head, you can select it from here as well.

  • FW: Select the active Filter Wheel device. If your camera has a built-in filter wheel, the device would be the same as the camera.

  • Cooler: Toggle Cooler On/Off. Set the desired temperature, if your camera is equipped with a cooler. Check the option to force temperature setting before any capture. Capture process is only started after the measured temperature is within requested temperature tolerance. The default tolerance is 0.1 degrees Celsius but can be adjusted in Capture options under Ekos configuration.

Capture Settings

Capture Settings

Set all capture parameters as detailed below. Once set, you can capture a preview by click on Preview or add a job to the sequence queue.

  • Exposure: Specify exposure duration in seconds.

  • Filter: Specify the desired filter.

  • Count: Number of images to capture

  • Delay: Delay in seconds between image captures.

  • Type: Specify the type of desired CCD frame. Options are Light, Dark, Bias, and Flat frames.

  • ISO: For DSLR cameras, specify the ISO value.

  • Format: Specify capture save format. For all CCDs, only FITS option is available. For DSLR cameras, you can an additional option to save in Native format (e.g. RAW or JPEG).

  • Custom Properties: Set extended properties available in the camera to the job settings.

  • Calibration: For Dark &s; Flat frames, you can set additional options explained in the Calibration Frames section below.

  • Frame: Specify the left (X), top (Y), width (W), and height (H) of the desired CCD frame. If you changed the frame dimensions, you can reset it to default values by clicking on the reset button.

  • Binning: Specify horizontal (X) and vertical (Y) binning.

Custom Properties

Many cameras offer additional properties that cannot be directly set in the capture settings using the common control. The capture controls described above represent the most common settings shared among different cameras, but each camera is unique and may offer its own extended properties. While you can use INDI Control Panel to set any property in the driver; it is important to be able to set such property for each job in the sequence. When you click Custom Properties, a dialog is shown divided into Available Properties and Job Properties. When you move an Available Properties to the Job Property list, its current value can be recorded once you click Apply. When you add a job to the Sequence Queue, the properties values selected in the Job Properties list shall be recorded and saved.

The following video explains this concept is more detail with a live example:

Custom Properties feature

File Settings

File Settings

Settings for specifying where captured images are saved to, and how to generate unique file names in addition to upload mode settings.

  • Prefix: Specify the prefix to append to the generated filename. You may also append the frame type, filter, expose duration, and ISO 8601 timestamp. For example, if you specify Prefix as M45 and checked the Type and Filter checkboxes, and assuming your filter was set to Red and your frame type is Light, the generated file names will be as follows:

    • M45_Light_Red_001.fits

    • M45_Light_Red_002.fits

    If TS was checked, a timestamp will be appended to the filename, e.g.

    • M45_Light_Red_001_2016-11-09T23-47-46.fits

    • M45_Light_Red_002_2016-11-09T23-48-34.fits

  • Script: Specify an optional script to be executed after each capture is complete. The full path of the script must be specified and it must executable. To denote success, the script must return zero as this would allow the sequence to continue. If a non-zero value is returned by the script, the sequence is aborted.

  • Directory: Local directory to save the sequence images to.

  • Upload: Select how captured images are uploaded:

    1. Client: Captured images are only uploaded to Ekos and saved to the local directory specified above.

    2. Local: Captured images are only saved locally on the remote computer.

    3. Both: Captured images are saved on the remote device and uploaded to Ekos.

    When selecting Local or Both, you must specify the remote directory where the remote images are saved to. By default, all captured images are uploaded to Ekos.

  • Remote: When selecting either Local or Both modes above, you must specify the remote directory where remote images are saved to.

Limit Settings

Limit Settings

Limit settings are applicable to all the images in the sequence queue. When a limit is exceeded, Ekos shall command the appropriate action to remedy the situation as explained below.

  • Guiding Deviation: If checked, it enforces a limit of maximum allowable guiding deviation for the exposure, if autoguiding is used. If the guiding deviation exceeds this limit in arcseconds, it aborts the exposure sequence. It will automatically resume the exposure sequence again once the guiding deviation goes below this limit.

  • Autofocus if HFR >: If autofocus is enabled in the focus module and at least one autofocus operation was completed successfully, you can set the maximum acceptable HFR value. If this option is enabled then between consecutive exposures, the HFR value is recalculated, and if found to exceed the maximum acceptable HFR value, then an autofocus operation is automatically triggered. If the autofocus operation is completed successfully, the sequence queue resumes, otherwise, the job is aborted.

  • Meridian Flip: If supported by the mount, set the hour angle limit (in hours) before a meridian flip is commanded. For example, if you set the meridian flip duration to 0.1 hours, Ekos shall wait until the mount passes the meridian by 0.1 hours (6 minutes), then it commands the mount to perform a meridian flip. After the meridian flip is complete, Ekos re-aligns using astrometry.net (if the alignment was used) and resumes guiding (if it was started before) and then resumes the capture process automatically.

Sequence Queue

Sequence Queue is the primary hub of the Ekos Capture Module. This is where you can plan and execute jobs using the sequence queue built-in powerful editor. To add a job, simply select all the parameters from the capture and file settings as indicated above. Once you selected your desired parameters, click on the add button in the sequence queue to add it to the queue.

Sequence Queue

You can add as many jobs as desired. While it is not strictly necessary, it is preferable to add the dark and flat jobs after the light frames. Once you are done adding jobs, simply click Start Sequence to begin executing the jobs. A job state changes from Idle to In Progress and finally to Complete once it is done. The Sequence Queue automatically starts the next job. If a job is aborted, it may be resumed again. To pause a sequence, click the pause button and the sequence will be stopped after the current capture is complete. To reset the status of all the jobs, simply click the reset button . Please beware that all image progress counts are reset as well. To preview an image in KStars FITS Viewer, click the Preview button.

Sequence queues can be saved as an XML file with extension .esq (Ekos Sequence Queue). To load a sequence queue, click the open document button . Please note that it will replace any current sequence queues in Ekos.


Job Progress: Ekos is designed to execute and resume the sequence over multiple nights if required. Therefore, if Remember Job Progress option is enabled in Ekos Options, Ekos shall scan the file system to count how many images are already completed and will resume the sequence from where it was left off. If this default behavior is not desired, simply turn off Remember Job Progress under options.

To edit a job, double click it. You will notice the add button now changed to check mark button . Make your changes on the left-hand side of the CCD module and once done, click on the check mark button. To cancel a job edit, click anywhere on the empty space within the sequence queue table.

If your camera supports live video feed, then you can click the Live Video button to start streaming. The video stream window enables recording and subframing of the video stream. For more information, check the video below:

Recording feature

Filter Settings

Filter Queue

Click the filter icon next to the filter wheel selection box to open the filter settings dialog. If you are using filters that are not parafocal with each other and require a specific amount of focus offsets in order to get them into proper then set all the relative focus offsets in the dialog.

Configure settings for each filter individually:

  1. Filter: Filter Name.

  2. Exposure: Set exposure time used when performing focus under this filter. By default, it is set to 1 second.

  3. Offset: Set relative offsets. Ekos will command a focus offset change if there is a difference between the current and target filter offsets. For example, given the values in the example image, if the current filter is set to Red and next filter is Green, then Ekos shall command the focuser to Focus In by +300 ticks. Relative positive focus offsets denote Focus Out while negative values denote Focus In.

  4. Auto Focus: Check this option to initial AutoFocus process whenever the filter is changed to this filter.

  5. Lock Filter: Set which filter should be set and locked when performing autofocus for this filter.

Let's take an example. Suppose the capture sequence is running and the current filter is Green, so the relative offset is already set to +300. The next image in the sequence uses Hydrogen Alpha (H_Alpha) so before Ekos captures the next frame, the following actions take place:

  • Since Luminosity is specified as the locked filter and auto-focus is checked, the filter is changed to Luminosity.

  • A focus offset is -300 is applied since the prior filter Green was moved +300 previously.

  • Auto Focus process is initiated.

  • Once Auto Focus is complete, the filter is changed to H_Alpha.

  • A focus offset of -1200 is applied.

  • Capture sequence is resumed.

FITS Viewer

Captured images are displayed in KStars FITS Viewer tool, and also in the summary screen. Set options related to how the images are displayed in the viewer.

  • Auto Dark: You can capture an image and auto dark subtract it by checking this option. Note that this option is only applicable when using Preview, you cannot use it in batch mode sequence queue.

  • Effects: Image enhancement filter to be applied to the image after capture.

Rotator Settings

Rotator Settings

Field Rotators are supported in INDI & Ekos. The rotator angle is the raw angle reported by the rotator and is not necessary the Position Angle. A Position Angle of zero indicates that the frame top (indicated by small arrow) is pointing directly at the pole. The position angle is expressed as E of N (East of North), so 90 degrees PA indicates the frame top points 90 degrees away (counter-clockwise) from the pole. Check examples for various PAs.

To calibrate the Position Angle (PA), capture and solve an image in the Ekos Align module. An offset and a multiplier are applied to the raw angle to produce the position angle. The Ekos Rotator dialog permits direct control of the raw angle and also the PA. The offset and multiplier can be changed manually to synchronize the rotator's raw angle with the actual PA. Check Sync FOV to PA to rotate the current Field of View (FOV) indicator on the Sky Map with the PA value as you change it in the dialog.

Rotator settings

Each capture job may be assigned different rotator angles, but be aware that this would cause guiding to abort as it would lose track of the guide star when rotating. Therefore, for most sequences, the rotator angle is kept the same for all capture jobs.

Calibration Frames

Calibration settings

For Flat Field frames, you can set calibration options in order to automate the process. The calibration options are designed to facilitate automatic unattended flat field frame capture. It can also be used for dark and bias frames if desired. If your camera is equipped with a mechanical shutter, then it is not necessary to set calibration settings unless you want to close the dust cover to ensure no light at all passes through the optical tube. For flat fields, you must specify the flat field light source, and then specify the duration of the flat field frame. The duration can be either manual or based on ADU calculations.

  1. Flat Field Source

    • Manual: The flat light source is manual.

    • Dust Cover with Built-In Flat Light: If using a dust cover with builtin light source (e.g. FlipFlat). For dark and bias frames, close the dust cap before proceeding. For flat frames, close the dust cap and turn on the light source.

    • Dust Cover with External Flat Light: If using a dust cover with an external flat light source. For dark and bias frames, close the dust cap before proceeding. For flat frames, open the dust cap and turn on the light source. The external flat light source location is presumed to be the parking location.

    • Wall: Light source is a panel on the observatory wall. Specify the Azimuth and Altitude coordinates of the panel and the mount shall slew there before capturing the flat field frames. If the light panel is controllable from INDI, Ekos shall turn it on/off as required.

    • Dawn/Dusk: Currently unsupported.

  2. Flat Field Duration

    • Manual: Duration is as specified in the Sequence Queue.

    • ADU: Duration is variable until specified ADU is met.

Before the calibration capture process is started, you can request Ekos to park the mount and/or dome. Depending on your flat source selection above, Ekos will use the appropriate flat light source before starting flat frames capture. If ADU is specified, Ekos begins by capturing a couple of preview images to establish the curve required to achieve the desired ADU count. Once an appropriate value is calculated, another capture is taken and ADU is recounted until a satisfactory value is achieved.

Video Tutorials


Filter Wheels


Theory Of Operation

Ekos Focus

In order to focus an image, Ekos needs to establish a numerical method for gauging how good your focus is. It's easy when you look at an image and can see it as unfocused, as the human is very good at detecting that, but how can Ekos possibly know that?

There are multiple methods. One is to calculate the Full Width at Half Maximum (FHWM) of a star profile within an image, and then adjust the focus until an optimal (narrower) FWHM is reached. The problem with FWHM is that it assumes the initial focus position to be close to the critical focus. Additionally, FWHM does not perform very well under low-intensity fluxes. An Alternative method is Half-Flux-Radius (HFR), which is a measure of the width in pixels counting from the center of the stars until the accumulated intensity is half of the total flux of the star. HFR proved to be much more stable in conditions where you might have unfavorable sky conditions, when the brightness profile of the stars is low, and when the starting position of the focus is far from the optimal focus.

After Ekos processes an image, it selects the brightest star and starts measuring its HFR. It can automatically select the star, or you can select the star manually. It is usually recommended to select stars that are not too bright as they might get saturated during the focusing process. A magnitude 3 or 4 star is often sufficient.

Ekos then begins the focusing process by commanding the focuser to focus inwards or outwards, and re-measures the HFR. This establishes a V-shaped curve in which the sweet spot of optimal focus is at the center of the V-curve, and the slope of which depends on the properties of the telescope and camera in use. In Ekos, a full V-curve is never constructed as the focusing process works iteratively, so under most circumstances, a half V-curve shape as illustrated in the Focus Module image is measured.

Because the HFR varies linearly with focus distance, it is possible to calculate the optimal focus point. In practice, Ekos operates iteratively by moving in discrete steps, decided initially by the user-configurable step size and later by the slope of the V-curve, to get closer to the optimal focus position where it then changes gears and performs smaller, finer moves to reach the optimal focus. In the default Iterative algorithm, the focus process stops when the measured HFR is within the configurable tolerance of the minimum recorded HFR in the process. In other words, whenever the process starts searching for a solution within a narrowly limited range, it checks if the current HFR is within % difference compared to the minimum HFR recorded, and if this condition is met then the autofocus process is considered successful. The default value is set to 1% and is sufficient for most situations. The Step options specify the number of initial ticks the focuser has to move. If the image is severely out of focus, we set the step size high (i.e. > 250). On the other hand, if the focus is close to optimal focus, we set the step size to a more reasonable range (< 50). It takes trial and error to find the best starting tick, but Ekos only uses that for the first focus motion, as all subsequent motions depend on the V-Curve slope calculations.

When using the Polynomial algorithm, the process starts in the Iterative mode, but once we cross to the other side of the V-curve (i.e. once HFR values start increasing again after decreasing for a while), the Ekos performs polynomial fitting to find a solution that predicts the minimum possible HFR position. If a valid solution is found, the autofocus process is considered successful.

While Ekos Focus Module supports relative focusers, it is highly recommended to use absolute focusers.

Focuser Group

Focuser Settings

Any INDI-compatible focuser is supported. It is recommended to use absolute focusers since their absolute position is known on power up. In INDI, the focuser zero position is when the drawtube is fully retracted. When focusing outwards, the focuser position increases, while it decreases when focusing inwards. The following focuser types are supported:

  • Absolute: Absolute Position Focusers such as RoboFocus, MoonLite, etc.

  • Relative: Relative Position Focusers.

  • Simple Focusers: DC/PWM focusers with no position feedback.

For absolute focusers, you can set the ticks count. To view a continuous feed of the camera, click the Framing button. An image shall be captured repeatedly according to the CCD settings in the CCD and Filter Wheel group. You can focus in and out by pressing the respective buttons, and each shall move by the step size indicated in the focus settings. For absolute and relative focusers, the step size is in units of ticks and for simple DC focusers, the step size is in milliseconds.

To begin the autofocus process, simply click the Auto Focus button.

CCD & Filter Wheel Group

Focus CCD & Filter Wheel Group

You must specify the CCD and Filter Wheel (if any) to be used during the focusing process. You can lock a specific filter within the filter wheel to be utilized whenever the autofocus process is invoked. Usually, the user should select the Clear/Luminescence filter for this purpose so that Ekos always uses the same filter to perform the autofocus process. This locked filter is also used in the Alignment Module whenever it performs any astrometry capture.

You may also select an Effect filter to enhance the image for preview purposes. It is highly advisable to turn off any effects during the focusing process as it may interfere with HFR calculations. For DSLRs cameras, you can change the ISO settings. You may reset the focusing subframe to full frame capture if you click the Reset button.


Focus Settings

You may need to adjust focus settings in order to achieve a successful and reliable autofocus process. The settings are retained between sessions.

  • Auto Star Select: Automatically select the best focus star from the image.

  • Subframe: Subframe around the focus star during the autofocus procedure. Enabling subframing can significantly speed up the focus process.

  • Dark Frame: Check this option to capture a dark frame if necessary and perform dark-frame subtraction. This option can be useful in noisy images.

  • Suspend Guiding: Suspend Guiding while autofocus in progress. If the focus process can disrupt the guide star (e.g. when using Integrated Guide Port IGP whereas the guider is physically attached to the primary CCD), then it is recommended to enable this option. When using Off-Axis guider, then this option is not necessary.

  • Box size: Sets the box size used to enclose the focus star. Increase if you have very large stars. For Bahtinov focus the box size can be increased even more to better enclose the Bahtinov diffraction pattern.

  • Max Travel: Maximum travel in ticks before the autofocus process aborts.

  • Step: Initial step size in ticks to cause a noticeable change in HFR value. For timer-based focuser, it is the initial time in milliseconds to move the focuser inward or outward.

  • Tolerance: The tolerance percentage values decides when the autofocus process stops in the Iterative algorithm. During the autofocus process, HFR values are recorded, and once the focuser is close to an optimal position, it starts measuring HFRs against the minimum recorded HFR in the sessions and stops whenever a measured HFR value is within % difference of the minimum recorded HFR. Decrease value to narrow optimal focus point solution radius. Increase to expand solution radius.


    Setting the value too low might result in a repetitive loop and would most likely result in a failed autofocus process.

  • Threshold: Threshold percentage value is used for star detection using the Threshold detection algorithm. Increase to restrict the centroid to bright cores. Decrease to enclose fuzzy stars.

  • Algorithm: Select the autofocus process algorithm:

    • Iterative: Moves focuser by discreet steps initially decided by the step size. Once a curve slope is calculated, further step sizes are calculated to reach an optimal solution. The algorithm stops when the measured HFR is within percentage tolerance of the minimum HFR recorded in the procedure.

    • Polynomial: Starts with the iterative method. Upon crossing to the other side of the V-Curve, polynomial fitting coefficients along with possible minimum solution are calculated. This algorithm can be faster than a purely iterative approach given a good data set.

  • Frames: Number of average frames to capture. During each capture, an HFR is recorded. If the instantaneous HFR value is unreliable, you can average a number of frames to increase the signal to noise ratio.

  • Detection: Select star detection algorithm. Each algorithm has its strengths and weaknesses. It is recommended to keep the default value unless it fails to properly detect stars.

    • Bahtinov: This detection method can be used when using a Bahtinov mask for focusing. First take an image, then select the star to focus on. A new image will be taken and the diffraction pattern will be analysed. Three lines will be displayed on the diffraction pattern showing how well the pattern is recognized and how good the image is in focus. When the pattern is not well recognized, the 'Num. of rows' parameter can be adjusted to improve recognition. The line with the circles at each end is a magnified indicator for the focus. The shorter the line, the better the image is in focus.


Focus V-Curve

The V-shaped curve displays absolute position versus Half-Flux-Radius (HFR) values. The center of the V-curve is the optimal focus position. Once Ekos crosses from one side of the V-curve to the other, it backtracks and tries to find the optimal focus position. The final focus position is decided by which algorithm is selected.

When framing, the horizontal axis denotes the frame number. This is to aid you in the framing process as you can see how HFR changes between frames.

Relative Profile

Focus Relative Profile

The relative profile is a graph that displays the relative HFR values plotted against each other. Lower HFR values correspond to narrower shapes and vice-versa. The solid red curve is the profile of the current HFR value, while the dotted green curve is for the previous HFR value. Finally, the magenta curve denotes the first measured HFR and is displayed when the autofocus process concludes. This enables you to judge how well the autofocus process improved the relative focus quality.


Ekos Guide Module


Ekos Guide Module enables autoguiding capability using either the powerful built-in guider, or at your option, external guiding via PHD2 or lin_guider. Using the internal guiding, guider CCD frames are captured and sent to Ekos for analysis. Depending on the deviations of the guide star from its lock position, guiding pulses corrections are sent to your mount Via any device that supports ST4 ports. Alternatively, you may send the corrections to your mount directly, if supported by the mount driver. Most of the GUI options in the Guide Module are well documented so just hover your mouse over an item and a tooltip will popup with helpful information.

To perform guiding, you need to select a Guider CCD in Ekos Profile Setup. The telescope aperture and focal length must be set in the telescope driver. If the Guider CCD is attached to a separate Guide Scope, you must also set the Guide Scope's Focal Length and Aperture. You can set these values under the Options tab of the telescope driver or from the Mount module. Autoguiding is a two-step process: Calibration & Guiding.

Guiding introduction

During the two processes, you must set the following:

  • Guider: Select the Guider CCD.

  • Via: Selects which device receives the autoguiding correction pulses from Ekos. Usually, guider CCDs have an ST4 port. If you are using the guider's ST4 to autoguide your telescope, set the guider driver in the Via combo box. The guider CCD will receive the correction pulses from Ekos and will relay them to the mount via the ST4 port. Alternatively, some telescopes support pulse commands and you can select the telescope to be a receiver of the Ekos correction pulses.

  • Exposure: CCD Exposure in seconds.

  • Binning: CCD Binning.

  • Box: Size of the box enclosing the guide star. Select a suitable size that is neither too large or too small for the selected star.

  • Effects: Specify filter to be applied to the image to enhance it.

Dark Frames

Dark frames are immensely helpful in reducing noises in your guide frames. It is highly recommended to take dark frames before you begin and calibration or guiding procedure. To take a dark frame, check the Dark checkbox and then click Capture. For the first time this is performed, Ekos will ask you about your camera shutter. If your camera does not have a shutter, then Ekos will warn you anytime you take a dark frame to cover your camera/telescope before proceeding with the capture. On the other hand, if the camera already includes a shutter, then Ekos will directly proceed with taking the dark frame. All dark frames are automatically saved to Ekos Dark Frame Library. By default, the Dark Library keeps reusing dark frames for 30 days after which it will capture new dark frames. This value is configurable and can be adjusted in Ekos settings in the KStars settings dialog.

Ekos Dark frames library

It is recommended to take dark frames covering several binning and exposure values so that they may be reused transparently by Ekos whenever needed.


Calibration Settings

In the calibration phase, you need to capture an image, select a guide star, and click Guide to begin the calibration process. If calibration was already completed successfully before, then the autoguiding process shall begin immediately, otherwise, it would start the calibration process. If Auto Star is checked, then you are only required to click Capture and Ekos will automatically select the best-fit guide star in the image and continues the calibration process automatically. If Auto Star is disabled, Ekos will try to automatically highlight the best guide star in the field. You need to confirm or change the selection before you can start the calibration process. The calibration options are:

  • Pulse: The duration of pulses in milliseconds to be sent to the mount. This value should be large enough to cause a noticeable movement in the guide star. If you increase the value and you do not notice any movement of the guide star, then this suggests possible mount issues such as jamming or connection issues via the ST4 cable.

  • Two axis: Check if you want the calibration process makes calibration in both RA & DEC. If unchecked, the calibration is only performed in RA.

  • Auto Star: If checked, Ekos will attempt to select the best guide star in the frame and begins the calibration process automatically.

The reticle position is the guide star position selected by you (or by the auto selection) in the captured guider image. You should select a star that is not close to the edge. If the image is not clear, you may select different Effects to enhance it.

Ekos begins the calibration process by sending pulses to move the mount in RA and DEC. If the calibration process fails due to short drift, try increasing the pulse duration. To clear calibration, click the trash bin icon next to the Guide button.


Calibration can fail for a variety of reasons. To improve the chances of success, try the tips below.

  • Better Polar Alignment: This is critical to the success of any astrophotography session. Perform a quick polar alignment with a polar scope (if available) or by using Ekos Polar Alignment procedure in the Align module.

  • Set binning to 2x2: Binning improves SNR and is often very important to the success of the calibration and guiding procedures.

  • Prefer to use ST4 cable between guide-camera and mount over using mount pulse commands.

  • Select different filter (e.g. High contrast) and see if that makes a difference to bring down the noise.

  • Smaller Square Size.

  • Take dark frames to reduce noise.

  • Play with DEC Proportional Gain or disable DEC control completely and see the difference.

  • Leave algorithm to the default value (Smart).


Guide Settings

Once the calibration process is completed successfully, the guiding shall begin automatically hereafter. The guiding performance is displayed in the Drift Graphics region where Green reflects deviations in RA and Blue deviations in DEC. The colors of the RA/DE lines can be changed in KStars color scheme in KStars settings dialog. The vertical axis denotes the deviation in arcsecs from the guide star central position and the horizontal axis denotes time. You can hover over the line to get the exact deviation at this particular point in time. Furthermore, you can also zoom and drag/pan the graph to inspect a specific region of the graph.

Ekos can utilize multiple algorithms to determine the center of mass of the guide star. By default, the smart algorithm is suited best for most situation. The fast algorithm is based on HFR calculations. You can try switching guiding algorithms if Ekos cannot keep of the guide star within the guiding square properly.

The info region displays information on the telescope & FOV, in addition to the deviations from the guide star along with the correction pulses sent to the mount. The RMS value for each axis is displayed along with the total RMS value in arcsecs. The internal guider employs PID controller to correct the mount tracking. Currently, the only the proportional and integral gains are utilized within the algorithm, so adjusting it should affect the length of the generated pulses sent to the mount in milliseconds.

To enable automatic dithering between frames, make sure to check the Dither checkbox. By default, Ekos should dither (i.e. move) the guiding box by up to 3 pixels after each frame captured in Ekos Capture Module. The motion duration and direction are randomized. Since the guiding performance can oscillate immediately after dithering, you can set the appropriate Settle duration to wait after dither is complete before resuming the capture process. In rare cases where the dithering process can get stuck in an endless loop, set the appropriate Timeout to abort the process. But even if dithering fails, you can select whether this failure should terminate the autoguiding process or not. Toggle Abort Autoguide on failure to select the desired behavior.

Non-guide dithering is also supported. This is useful when no guide camera is available or when performing short exposures. In this case, the mount can be commanded to dither in a random direction for up to the pulse specified in the Non-Guide Dither Pulse option.

Ekos supports multiple guiding methods: Internal, PHD2, and LinGuider. You need to select the desired guider in your Ekos equipment profile:

  • Internal Guider: Use Ekos internal guider. This is the default and recommended option.

  • PHD2: Use PHD2 as the external guider. If selected, specify the host and port of the PHD2. Leave to default values if Ekos and PHD2 are running on the same machine.

  • LinGuider: Use LinGuider as the external guider. If selected, specify the host and port of the LinGuider. Leave to default values if Ekos and LinGuider are running on the same machine.

Guiding Direction Control

Guiding Direction Control

You can fine-tune the guiding performance in the Control Section. The autoguide process works like a PID controller when sending correction commands to the mount. You can alter the Proportional and Integral gains to improve the guiding performance if necessary. By default, guiding corrective pulses are sent to both mount axis in all directions: positive and negative. You can fine-tune control by selecting which axis shall receive corrective guiding pulses and within each axis, you can indicate which direction (Positive) + or Negative (-) receives the guiding pulses. For example, for the Declination axis, the + direction is North and - is South.

Guiding Rate

Each mount has a particular guiding rate in (x15"/sec) and usually ranges from 0.1x, to 1.0x with 0.5x being a common value used by many mounts. The default guiding rate is 0.5x sidereal, which is equivalent to a proportional gain of 133.33. Therefore, set the guiding rate value to whatever value used by your mount, and Ekos shall display the recommended proportional gain value that you may set in the proportional gain field under the Control Parameters. Setting this value does not change your mount guiding rate! You must change your mount guiding rate either via the INDI driver, if supported, or via the hand controller.

Drift Graphics

Drift Graphics

The drift graphics is a very useful tool to monitor the guiding performance. It is a 2D plot of guiding deviations and corrections. By default, only the guiding deviations in RA and DE are displayed. The horizontal axis is the time in seconds since the autoguiding process was started while the vertical axis plots the guiding drift/deviation in arcsecs for each axis. Guiding corrections (pulses) can also be plotted in the same graph and you can enable them by checking the Corr checkbox below each Axis. The corrections are plotted as shaded areas in the background with the same color as that of the axis.

You can pan and zoom the plot, and when hovering the mouse over the graph, a tooltip is displayed containing information about this specific point in time. It contains the guiding drift and any corrections made, in addition to the local time, this event was recorded. A vertical slider to the right of the image can be used to adjust the height of the secondary Y-axis for pulses corrections.

The Trace horizontal slider at the bottom can be used to scroll through the guide history. Alternatively, you can click the Max checkbox to lock the graph onto the latest point so that the drift graphics autoscrolls. The buttons to the right of the slider are used for autoscaling the graphs, exporting the guide data to a CSV file, clearing all the guide data, and for scaling the target in the Drift Plot. Furthermore, the guide graph includes a label to indicate when a dither occurred so the user knows guiding was not bad at those points.

The colors of each axis can be customized in KStars Settings color scheme.

Drift Plot

A bulls-eye scatter plot can be used to gauge the accuracy of the overall guiding performance. It is composed of three concentric rings of varying radii with the central green ring having a default radius of 2 arcsecs. The last RMS value is plotted as with its color reflecting which concentric ring it falls within. You can change the radius of the innermost green circle by adjusting the drift plot accuracy.

PHD2 Support

You can opt to select external PHD2 application to perform guiding instead of the built-in guider.

Ekos Guide PHD2 settings

If PHD2 is selected, the Connect and Disconnect buttons are enabled to allow you to establish a connection with the PHD2 server. You can control PHD2 exposure and DEC guide settings. When clicking Guide, PHD2 should perform all the required actions to start the guiding process. PHD2 must be started and configured before Ekos.

After launching PHD2, select your INDI equipment and set their options. From Ekos, connect to PHD2 by clicking the Connect button. On startup, Ekos will attempt to automatically connect to PHD2. Once the connection is established, you may begin the guiding immediately by click on the Guide button. PHD2 shall perform calibration if necessary. If dithering is selected, PHD2 shall be commanded to dither given the offset pixels indicated and once guiding is settled and stable, the capture process in Ekos shall resume.


Ekos saves a CSV guide log data that can be useful for analysis of the mount's performance under ~/.local/share/kstars/guide_log.txt. This log is only available when using the built-in guider.



Ekos Align Module

Ekos Alignment Module enables highly accurate GOTOs to within sub-arcseconds accuracy and can measure and correct polar alignment errors. This is possible thanks to the astrometry.net solver. Ekos begins by capturing an image of a star field, feeding that image to astrometry.net solver, and getting the central coordinates (RA, DEC) of the image. The solver essentially performs a pattern recognition against a catalog of millions of stars. Once the coordinates are determined, the true pointing of the telescope is known.

Often, there is a discrepancy between where the telescope thinks it is looking at and where it is truly pointing. The magnitude of this discrepancy can range from a few arcminutes to a couple of degrees. Ekos can then correct the discrepancy by either syncing to the new coordinates, or by slewing the mount to the desired target originally requested.

Furthermore, Ekos provides two tools to measure and correct polar alignment errors:

  • Polar Alignment Assistant Tool: A very easy tool to measure and correct polar errors. It takes three images near the celestial pole (Close to Polaris for Northern Hemisphere) and then calculates the offset between the mount axis and polar axis.

  • Legacy Polar Alignment Tool: If Polaris is not visible, this tool can be used to measure and correct polar alignment errors. It captures a couple of images near the meridian and east/west of the meridian. This will enable the user to adjust the mount until the misalignment is minimized.

At a minimum, you need a CCD/Webcam and a telescope that supports Slew & Sync commands. Most popular commercial telescope nowadays support such commands.

For the Ekos Alignment Module to work, you have an option of either utilizing the online astrometry.net solver, offline, or remote solver:

  • Online Solver: The online solver requires no configuration, and depending on your Internet bandwidth, it might take a while to upload and solve the image.

  • Offline Solver: The offline solver can be faster and requires no Internet connection. In order to use the offline solver, you must install astrometry.net in addition to the necessary index files.

  • Remote Solver: The remote solver is an offline solver the resides on a different machine (for example, you can use Astrometry solver on StellarMate). Captured images are solved on the remote machine.

Get astrometry.net

If you are planning to use Offline astrometry then you need to download astrometry.net application.


Astrometry.net is already shipped with StellarMate so there is no need to install it. Index files from 16 arcminutes and above (4206 to 4019) are included with StellarMate. For any additional index files, you need to install them as necessary. To use Astrometry in StellarMate from a remote Ekos on Linux®/Windows®/Mac® OS, make sure to select Remote option in Ekos Alignment Module. Furthermore, make sure that the Astrometry driver is selected in your equipment profile.

Ekos Remote Astrometry

To use astrometry.net under Windows®, you need to download and install the ANSVR Local Astrometry.net solver. The ANSVR mimics the astrometry.net online server on your local computer; thus the internet not required for any astrometry queries.

After installing the ANSVR server and downloading the appropriate index files for your setup, make sure ANSVR server is up and running and then go to Ekos Alignment options where you can simply change the API URL to use the ANSVR server as illustrated below:

ANSVR Parameters

In Ekos Align module, you must set the solver type to Online so that it uses the local ANSVR server for all astrometry queries. Then you can use the align module as you would normally do.

Remember as indicated above that StellarMate already includes astrometry.net. Therefore, if you would like to use StellarMate remotely to solve your images, simply change solver type to Remote and ensure that your equipment profile includes Astrometry driver which can be selected under the Auxiliary dropdown. This is applicable to all operating systems and not just Windows®.

Mac® OS

Astrometry.net is already included with KStars for Mac® OS, so no need to install it.


Astrometry.net is already included with KStars bleeding version. But if astrometry is not installed, then you can install it by running the following command under Ubuntu™:

sudo apt-get install astrometry.net

Download Index Files

For offline (and remote) solvers, index files are necessary for the solver to work. The complete collection of index files is huge (over 30 GB), but you only need to download what is necessary for your equipment setup. Index files are sorted by the Field-Of-View (FOV) range they cover. There are two methods to fetch the necessary index files: The new download support in Align module, and the old manual way.

Automatic Download
Astrometry.net Indexes Download

Automatic download is only available for Ekos users on Linux® & Mac® OS. For Windows® users, please download ANSVR solver.

To access the download page, click the Options button in the Align module and then select Astrometry Index Files tab. The page displays the current FOV of your current setup and below it a list of available and installed index files. Three icons are used to designate the importance of index files given your current setup as follows:

  • Required

  • Recommended

  • Optional

You must download all the required files, and if you have plenty of hard drive space left, you can also download the recommended indexes. If an index file is installed, the checkmark shall be checked, otherwise check it to download the relevant index file. Please only download one file at a time, especially for larger files. You might be prompted to enter the administrator password (default in StellarMate is smate) to install the files. Once you installed all the required files, you can begin using the offline astrometry.net solver immediately.

Manual Download

You need to download and install the necessary index files suitable for your telescope+CCD field of view (FOV). You need to install index files covering 100% to 10% of your FOV. For example, if your FOV is 60 arcminutes, you need to install index files covering skymarks from 6 arcminutes (10%) to 60 arcminutes (100%). There are many online tools to calculate FOVs, such as Starizona Field of View Calculator.

Table 5.1. Index Files

Index FilenameFOV (arcminutes)Debian Package
index-4219.fits1400 - 2000astrometry-data-4208-4219
index-4218.fits1000 - 1400
index-4217.fits680 - 1000
index-4216.fits480 - 680
index-4215.fits340 - 480
index-4214.fits240 - 340
index-4213.fits170 - 240
index-4212.fits120 - 170
index-4211.fits85 - 120
index-4210.fits60 - 85
index-4209.fits42 - 60
index-4208.fits30 - 42
index-4207-*.fits22 - 30astrometry-data-4207
index-4206-*.fits16 - 22astrometry-data-4206
index-4205-*.fits11 - 16astrometry-data-4205
index-4204-*.fits8 - 11astrometry-data-4204
index-4203-*.fits5.6 - 8.0astrometry-data-4203
index-4202-*.fits4.0 - 5.6astrometry-data-4202
index-4201-*.fits2.8 - 4.0astrometry-data-4201-1 astrometry-data-4201-2 astrometry-data-4201-3 astrometry-data-4201-4
index-4200-*.fits2.0 - 2.8astrometry-data-4200-1 astrometry-data-4200-2 astrometry-data-4200-3 astrometry-data-4200-4

The Debian packages are suitable for any Debian-based distribution (Ubuntu, Mint, etc.). If you downloaded the Debian Packages above for your FOV range, you can install them from your favorite package manager, or via the following command:

sudo dpkg -i astrometry-data-*.deb

On the other hand, if you downloaded the FITS index files directly, copy them to /usr/share/astrometry directory.


It is recommended to use a download manager as such DownThemAll! for Firefox to download the Debian packages as browsers' built-in download manager may have problems with download large packages.

How to Use?

Ekos Align Module offers multiple functions to aid you in achieving accurate GOTOs. Start with your mount in home position with the telescope tube looking directly at the celestial pole. For users in Northern Hemisphere, point the telescope as close as possible to Polaris. It is not necessary to perform 2 or 3 star alignments, but it can be useful for some mount types. Make sure your camera is focused and stars are resolved.

  • Capture & Solve: Capture an image and determine what region in the sky the telescope is exactly looking at. The astrometry results include the equatorial coordinates (RA & DEC) of the center of the captured image in addition to pixel scale and field rotation. Depending on the Solver Action settings, the results can be used to Sync the mount or Sync and then Slew to the target location. For example, suppose you slewed the mount to Vega then used Capture & Solve. If the actual telescope location is different from Vega, it will be first synced to the solved coordinate and then Ekos shall command the mount to slew to Vega. After slew is complete, the Alignment module will repeat Capture & Solve process again until the error between reported and actual position falls below the accuracy thresholds (30 arcseconds by default).

  • Load & Slew: Load a FITS or JPEG file, solve it, and then slew to it.

  • Polar Alignment Assistant: A simple tool to aid in polar alignment of German Equatorial Mounts.

  • Legacy Polar Alignment Tool: Measure polar alignment error when a view of the celestial pole (e.g. Polaris for Northern Hemisphere) is not available.


Never solve an image at or near the celestial pole (unless Ekos Polar Alignment Assistant Tool is used). Slew at least 20 degrees away from the celestial pole before solving the first image. Solving very close to the poles will make your mount pointing worse so avoid it.

Alignment Settings

Astrometry.net Settings

Before you begin the alignment process, select the desired CCD & Telescope. You can explore astrometry.net options that are passed to the astrometry.net solver each time an image is captured:

  • CCD: Select CCD to capture from.

  • Exposure: Exposure duration in seconds.

  • Accuracy: Acceptable difference between reported telescope coordinate and actually solved coordinate.

  • Bin X: Set horizontal binning of the CCD.

  • Bin Y: Set vertical binning of the CCD.

  • Scope: Set the active telescope in case you have different Primary and Guide scopes. FOV is re-calculated when selecting a different telescope.

  • Options: Options that are passed to the astrometry.net solver. Click the edit button to explore the options in detail.

  • Solver: Select solver type (Online, Offline, Remote). The remote solver is only available when connecting to a remote device.

By default, the solver will search all over the sky to determine the coordinates of the captured image. This can take a lot of time; therefore, in order to speed up the solver, you can restrict it to only search within a specified area in the sky designated by the RA, DEC, and Radius options above.

Astrometry.net Options

Options for offline and online solvers.

Astrometry.net Options

Most of the options are sufficient by default. If you have astrometry.net installed in a non-standard location, you can change the paths as necessary.

  • WCS: World-Coordinate-System is a system for embedding equatorial coordinate information within the image. Therefore, when you view the image, you can hover it and view the coordinate for each pixel. You can also click anywhere in the image and command to the telescope to slew there. It is highly recommended to keep this option on.

  • Verbose: If the solver repeatedly fails to solve, check this option to enable verbose output of the solver to help you identify any problems.

  • Overlay: Overlay captured images unto the sky map of KStars.

  • Upload JPG: When using online astrometry.net, upload all images are JPEGs to save bandwidth as FITS images can be large.

Solver Options

Ekos selects and updates the optimal options by default to accelerate the performance of the solver. You may opt to change the options that are passed to the solver in case the default options are not sufficient.

Solver Settings

Capture & Solve

Using Ekos Alignment Module, aligning your mount using the controller's 1, 2, or 3 star alignment is not strictly necessary, though for some mounts it is recommended to perform a rough 1 or 2 star alignment before using Ekos alignment module. If you are using EQMod, you can start using Ekos alignment module right away. A typical workflow for GOTO alignment involves the following steps:

  1. Set your mount to its home position (usually the NCP for equatorial mounts).

  2. Select Slew to Target in the Solver Action.

  3. Slew to a nearby bright star.

  4. After slew is complete, click Capture & Solve.

If the solver is successful, Ekos will sync and then slew to the star. The results are displayed in the Solution Results tab along with a bullseye diagram that shows the offset the reported telescope coordinates (i.e. where the telescope thinks it is looking at) vs. its actual position in the sky as determined by the solver.

Each time the solver is executed and returns successful results, Ekos can run on the following actions:

  • Sync: Syncs the telescope coordinates to the solution coordinates.

  • Slew to Target: Syncs the telescope coordinates to the solution coordinates and then slew to the target.

  • Nothing: Just solve the image and display the solution coordinates.

Polar Alignment

Polar Alignment Assistant

When setting up a German Equatorial Mount (GEM) for imaging, a critical aspect of capturing long-exposure images is to ensure proper polar alignment. A GEM mount has two axis: Right Ascension (RA) axis and Declination (DE) axis. Ideally, the RA axis should be aligned with the celestial sphere polar axis. A mount's job is to track the star's motion around the sky, from the moment they rise at the eastern horizon, all the way up across the median, and westward until they set.

Polar Alignment Assistant

In long exposure imaging, a camera is attached to the telescope where the image sensor captures incoming photons from a particular area in the sky. The incident photons have to strike the same photo-site over and over again if we are to gather a clear and crisp image. Of course, actual photons do not behave in this way: optics, atmosphere, seeing quality all scatter and refract photons in one way or another. Furthermore, photons do not arrive uniformly but follow a Poisson distribution. For point-like sources like stars, a point spread function describes how photons are spatially distributed across the pixels. Nevertheless, the overall idea we want to keep the source photons hitting the same pixels. Otherwise, we might end up with an image plagued with various trail artifacts.

Polar Alignment

Since mounts are not perfect, they cannot perfectly keep track of object as it transits across the sky. This can stem from many factors, one of which is the misalignment of the mount's Right Ascension axis with respect to the celestial pole axis. Polar alignment removes one of the biggest sources of tracking errors in the mount, but other sources of error still play a factor. If properly aligned, some mounts can track an object for a few minutes with the only deviation of 1-2 arcsec RMS.

However, unless you have a top of the line mount, then you'd probably want to use an autoguider to keep the same star locked in the same position over time. Despite all of this, if the axis of the mount is not properly aligned with the celestial pole, then even a mechanically-perfect mount would lose tracking with time. Tracking errors are proportional to the magnitude of the misalignment. It is therefore very important for long exposure imaging to get the mount polar aligned to reduce any residual errors as it spans across the sky.

Before starting the process, point the mount as close as possible to the celestial pole. If you are living in the Northern Hemisphere, point it as close as possible to Polaris.

The tool works by capturing and solving three images. After capturing each, the mount rotates by a fixed amount and another image is captured and solved.

Polar Alignment Assistant

After the first capture, you can rotate the mount by a specific amount (default 30 degrees) either West or East. After selecting the magnitude and direction, click Next to continue and the mount will be rotated. Once the rotation is complete you shall be asked to take another capture, unless you have checked Auto Mode. In Automated mode, the rest of the process will continue with the same settings and direction until a total of three images are captured.

Since the mount's true RA/DE are resolved by astrometry, we can construct a unique circle from the three centers found in the astrometry solutions. The circle's center is where the mount rotates about (RA Axis) and ideally, this point should coincide with the celestial pole. However, if there is a misalignment, then Ekos draws a correction vector. This correction vector can be placed anywhere in the image. Next, refresh the camera feed and make corrections to the mount's Altitude and Azimuth knobs until the star is located in the designated cross-hair. To make it easy to make corrections, expand the view by clicking on the Fullscreen button .

Polar Alignment Result

If you are away from StellarMate or PC, you can use your Tablet to monitor the camera feed while making corrections. Use the StellarMate's web-based VNC viewer or use any VNC Client on your tablet to access StellarMate. If Ekos is running on your PC, you can use applications like TeamViewer to achieve the same results. The following is a video demonstrating how to utilize the Polar Alignment Assistant tool.

Polar Alignment

Legacy Polar Alignment Workflow

Using the Polar Alignment mode, Ekos can measure and correct the polar alignment errors. To measure Azimuth error, point your mount to a star close to the meridian. If you live in the northern hemisphere, you will point the mount toward the southern meridian. Click on Measure Az Error to begin the process. Ekos will try to measure the drift between two images and calculates the error accordingly. You can ask Ekos to correct Azimuth error by clicking on the Correct Az Error button. Ekos will slew to a new location and asks you to adjust the mount's azimuth knobs until the star is in the center of the Field of View. You can use the Focus Module's Framing feature to take a look at the image as you make your adjustments.

Similarly, to measure Altitude error, click on the Measure Alt Error button. You need to point your mount either east or west and set the Altitude Direction combo box accordingly. Ekos will take two images and calculates the error. You can ask Ekos to correct Altitude error by clicking on the Correct Alt Error button. As with Azimuth correction, Ekos will slew to a new location and asks you to adjust the mount's altitude knobs until the star is in the center of the FOV.

After making a correction, it is recommended to measure the Azimuth and Altitude errors again and gauge the difference. You may need to perform the correction more than once to obtain optimal results.

Before starting the Polar Alignment tool, you must complete the GOTO Workflow above for at least one point in the sky. Once your mount is aligned, proceed with the following (assuming you live in the northern hemisphere):

  1. Slew to a bright star (4th magnitude or below) near the southern meridian (Azimuth 180). Make sure Slew to Target is selected. Capture and solve. The star should be exactly centered in your CCD field of view.

  2. Switch mode to Polar Alignment. Click Measure Az Error. It will ask you to slew to a star at the southern meridian which we already done. Click Continue. Ekos will now perform the error calculation.

  3. If all goes well, the error is displayed in the output boxes. To correct for the error, click Correct Az Error. Ekos will now slew to a different point in the sky, and you will be required to ONLY adjust the mount's azimuth knobs to center the star in the field of view. The most convenient way of monitoring the star field is by going to the Focus module and clicking Start Framing. If the azimuth error is great, the star might not be visible in the CCD field of view, and therefore you have to make blind adjustments (or simply look through the finderscope) until the star enters the CCD FOV.

  4. Begin your azimuth adjustments until the bright star you slewed to initially is as close to center as you can get it.

  5. Stop Framing in the Focus module.

  6. Repeat the Measure Az Error to ensure we indeed corrected the error. You might have to run it more than once to ensure the results are valid.

  7. Switch mode to GOTO.

  8. Now slew to a bright star either on the eastern or western horizon, preferably above 20 degrees of altitude. It has to be as close as possible to the eastern (90 azimuth) or western (270) cardinal points.

  9. After slew is complete, capture and solve. The star should be dead center in the CCD FOV now.

  10. Switch mode to Polar Alignment.

  11. Click Measure Alt Error. It will ask you to slew to a star at either the eastern (Azimuth 90) or western (Azimuth 270) horizon which we already done. Click Continue. Ekos will now perform the error calculation.

  12. To correct for the error, click Correct Alt Error. Ekos will now slew to a different point in the sky, and you will be required to ONLY adjust the mount's altitude knobs to center the star in the field of view. Start framing as done before in the focus module to help you with the centering.

  13. After centering is complete, stop framing.

  14. Repeat the Measure Alt Error to ensure we indeed corrected the error. You might have to run it more than once to ensure the results are valid.

  15. Polar alignment is now complete!


The mount may slew to a dangerous position and you might risk hitting the tripod and/or other equipment. Carefully monitor the mount's motion. Use at your own risk.


Ekos Scheduler Module


Ekos Scheduler is an indispensable arsenal in building your robotic observatory. A Robotic observatory is an observatory composed of several subsystems that are orchestrated together to achieve a set of scientific objectives without human intervention. It is the only Ekos module that does not require Ekos to be started as it is utilized to start and stop Ekos. It is designed to be straightforward and intuitive. However, the scheduler should only be used after you mastered Ekos and knows all the quirks of your equipment. Since the complete process is automated, including focus, guiding, and meridian flip, all equipment should be thoroughly used with Ekos and all their parameters and settings adjusted to achieve the best result.

With Ekos, the user can utilize the powerful sequence queue to image batches of images for a particular target. In simple setups, the user is expected to focus the CCD, align the mount, frame the target, and start guiding before initiating the capture process. For more complex observatory environments, there are usually predefined custom procedures to be executed to prepare the observatory for imaging, and another set of procedures on shutdown. The user may plan to image one or more targets during the night and expects data to be ready by morning. In KStars, tools such as the Observation Planner and What's up Tonight help the user in selecting candidates for imaging. After selecting the desired candidates, the user can add them to the Ekos Scheduler list for evaluation. The user may also add the targets directly in Ekos scheduler or select a FITS file of a previous image.


Ekos Scheduler provides a simple interface to aid the user in setting the conditions and constraints required for an observation job. Each observation job is composed of the following:

  • Target name and coordinates: Select target from the Find Dialog or Add it from Observation Planner. You can also enter a custom name.

  • Optional FITS File: If a FITS file is specified, the astrometry solver shall solve the file and use the central RA/DEC as the target coordinates.

  • Sequence file: The sequence file is constructed in the Ekos Capture Module. It contains the number of images to capture, filters, temperature settings, prefixes, download directory, etc.

  • Priority: Set job priority in the range of 1 to 20 where 1 designates the highest priority and 20 the lowest priority. Priority is applied in calculating the weight used to select the next target to image.

  • Profile: Select which equipment profile to utilize when starting Ekos. If Ekos & INDI are already started and online, this selection is ignored.

  • Steps: The user selects which Ekos modules should be utilized in the observation job execution workflow.

  • Startup Conditions: Conditions that must be met before the observation job is started. Currently, the user may select to start as soon as possible, ASAP, or when the target is near or past culmination, or at a specific time.

  • Constraints: Constraints are conditions that must be met at all times during the observation job execution process. These include minimum target altitude, minimum moon separation, twilight observation, artificial horizon altitude constraints, and weather monitoring.

  • Completion Conditions: Conditions that trigger completion of the observation job. The default selection is to simply mark the observation job as complete once the sequence process is complete. Additional conditions enable the user to repeat the sequence process indefinitely or up until a specific time.

You must select the Target and Sequence before you can add a job to the Scheduler. When the scheduler starts, it evaluates all jobs in accord to the conditions and constraints specified and attempts to select the best job to execute. Selection of the job depends on a simple heuristic algorithm that scores each job given the conditions and constraints, each of which is weighted accordingly. If two targets have identical conditions and constraints, usually the higher priority target followed by higher altitude target is selected for execution. If no candidates are available at the current time, the scheduler goes into sleep mode and wakes up when the next job is ready for execution.

Scheduler + Planner

The description above only tackles the Data Acquisition stage of the observatory workflow. The overall procedure typically utilized in an observatory can be summarized in three primary stages:

  1. Startup

  2. Data Acquisition (including preprocessing and storage)

  3. Shutdown

Startup Procedure

Startup procedure is unique to each observatory but may include:

  • Turning on power to equipment

  • Running safety/sanity checks

  • Checking weather conditions

  • Turning off light

  • Fan/Light control

  • Unparking dome

  • Unparking mount

  • etc.

Ekos Scheduler only initiates the startup procedure once the startup time for the first observation job is close (default lead time is 5 minutes before startup time). Once the startup procedure is completed successfully, the scheduler picks the observation job target and starts the sequence process. If a startup script is specified, it shall be executed first.

Data Acquisition

Depending the on the user selection, the typical workflow proceeds as follows:

  • Slew mount to target. If a FITS file was specified, it first solves the files and slew to the file coordinates.

  • Auto-focus target. The autofocus process automatically selects the best star in the frame and runs the autofocus algorithm against it.

  • Perform plate solving, sync mount, and slew to target coordinates.

  • Perform post-alignment focusing since the frame might have moved during the plate solving process.

  • Perform calibration and start auto-guiding: The calibration process automatically selects the best guide star, performs calibration, and starts the autoguide process.

  • Load the sequence file in the Capture module and start the imaging process.


Once the observation job is completed successfully, the scheduler selects the next target. If the next target scheduled time is not due yet, the mount is parked until the target is ready. Furthermore, if the next scheduled target is not due for a user-configurable time limit, the scheduler performs a preemptive shutdown to preserve resources and performs the startup procedure again when the target is due.

If an unrecoverable error occurs, the observatory initiates shutdown procedure. If there is a shutdown script, it will be executed last.

The following video demonstrates an earlier version of the scheduler, but the basic principles still apply today:

Ekos Scheduler

Weather Monitoring

Another critical feature of any remotely operated robotic observatory is weather monitoring. For weather updates, Ekos relies on the selected INDI weather driver to continuously monitor the weather conditions. For simplicity sake, the weather conditions can be summed in three states:

  1. Ok: Weather conditions are clear and optimal for imaging.

  2. Warning: Weather conditions are not clear, seeing is subpar, or partially obstructed and not suitable for imaging. Any further imaging process is suspended until the weather improves. Warning weather status does not pose any danger to the observatory equipment so the observatory is kept operational. The exact behavior to take under Warning status can be configured.

  3. Alert: Weather conditions are detrimental to the observatory safety and shutdown must be initiated as soon as possible.

Startup & Shutdown Scripts

Due to the uniqueness of each observatory, Ekos enables the user to select startup and shutdown scripts. The scripts take care of any necessary procedures that must take place on startup and shutdown stages. On startup, Ekos executes the startup scripts and only proceeds to the remainder of the startup procedure (unpark dome/unpark mount) if the script completes successfully. Conversely, the shutdown procedure begins with parking the mount & dome before executing the shutdown script as the final procedure.

Startup and shutdown scripts can be written any language that can be executed on the local machine. It must return 0 to report success, any other exist value is considered an error indicator. The script's standard output is also directed to Ekos logger window. The following is an sample demo startup script in Python:

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import os
import time
import sys

print "Turning on observatory equipment..."


print "Checking safety switches..."


print "All systems are GO"


The startup and shutdown scripts must be executable in order for Ekos to invoke them (e.g. use chmod +x startup_script.py to mark the script as executable). Ekos Scheduler enables truly simple robotic operation without the need of any human intervention in any step of the process. Without human presence, it becomes increasingly critical to gracefully recover from failures in any stage of the observation run. Using Plasma™ notifications, the user can configure audible alarms and email notifications for the various events in the scheduler.

Mosaic Wizard

Mosaic Wizard

Hubble-like super wide field images of galaxies and nebulae are truly awe-inspiring, and while it takes great skills to obtain such images and process them; many notable names in the field of astrophotography employ gear that is not vastly different from yours or mine. I emphasize vastly because some do indeed have impressive equipment and dedicated observatories worth tens of the thousands of dollars. Nevertheless, many amateurs can obtain stellar wide-field images by combining smaller images into a single grand mosaic.

We are often limited by our camera+telescope Field of View (FOV). By increasing FOV by means of a focal reducer or a shorter tube, we gain a larger sky coverage at the expense of spatial resolution. At the same time, many attractive wide-field targets span multiple FOVs across the sky. Without any changes to your astrophotography gear, it is possible to create a super mosaic image stitched together from several smaller images. There are two major steps to accomplish a super mosaic image:

  1. Capture multiple images spanning the target with some overlap between images. The overlap is necessary to enable the processing software from aligning and joining the sub-images.

  2. Process the images and stitch them into a super mosaic image.

The 2nd step is handled by image processing applications such as PixInsight, among others, and will not be the topic of discussion here. The first step can be accomplished in Ekos Scheduler where it creates a mosaic suitable for your equipment and in accordance with the desired field of view. Not only Ekos creates the mosaic panels for your target, but it also constructs the corresponding observatory jobs required to capture all the images. This greatly facilitates the logistics of capturing many images with different filters and calibration frames across a wide area of the sky.

Before starting the Mosaic Job Creator in Ekos Scheduler, you need to select a target and a sequence file. The Sequence File contains all the information necessary to capture an image including exposure time, filters, temperature setting, etc. Check that all the observation job conditions, constraints, and startup/shutdown procedures are as per your requirements since these settings shall be copied to all the jobs generated by the Mosaic tool. You do not need to add a job with this information ; if you added jobs to the observation list previously, Ekos will ask you if you would want to keep them before inserting the mosaic jobs in the list.

Start the Mosaic Job Creator by clicking on the icon next to the Find button in Ekos Module. A new window will open with a left-side form and your target centered in a sky chart. For convenience, maximize that window. There is a help icon on the top left part of the sky chart. Move your mouse over it to display the latest documentation of the tool.

On first use, you need to enter your equipment settings including your telescope focal length in addition to camera's width, height, and pixel dimensions. Finally, you need to enter the rotation of the camera with respect to north or the position angle. If you don't know this value, start Ekos and slew to your desired target then use the Align module to solve the image and obtain the position angle.

Next, enter the desired overlap and number of horizontal and vertical panels (e.g. 2x2, 3x3, etc.). The sky chart will update automatically after a short time, with target FOV calculated given the number of panels and your camera's FOV. By default, the percentage of the overlap among images is 5%, but you can change this value to your desired value. If you need to move the mosaic, close the tool and select a new target in the Scheduler. When satisfied, set the frequency of alignment and focus steps during the mosaic execution, choose an output folder and accept the dialog. Ekos shall create an observation job and a corresponding customized sequence file for each panel. All the jobs shall be saved to an Ekos Scheduler List (.esl) file that you can load on any suitable observing night and it will pick off where you left.

With Ekos Scheduler, multi-night imaging is greatly facilitated and creating super mosaics has never been so easy.


Ekos Analyze Module


The Analyze Module records and displays what happened in an imaging session. That is, it does not control any if your imaging, but rather reviews what occurred. Sessions are stored in an analyze folder, a sister folder to the main logging folder. The .analyze files written there can be loaded into the Analyze tab to be viewed. Analyze also can display data from the current imaging session.

There are two main graphs, Timeline and Stats. They are coordinated—they always display the same time interval from the Ekos session, though the x-axis of the Timeline shows seconds elapsed from the start of the log, and Stats shows clock time. The x-axis can be zoomed in and out with the +/- button, mouse wheel, as well as with standard keyboard shortcuts (e.g. zoom-in == Ctrl++) The x-axis can be panned with the scroll bar as well as with the left and right arrow keys. You can view your current imaging session, or review old sessions by loading .analyze files using the Input dropdown. Checking Full Width displays all the data, and Latest displays the most recent data (you can control the width by zooming).


Timeline shows the major Ekos processes, and when they were active. For instance, the Capture line shows when images were taken (green sections) and when imaging was aborted (red sections). Clicking on a green section gives information about that image, and double clicking on one brings up the image taken then in a fitsviewer, if it is available.


If you have moved your captured images, you can set alternate directory in the input menu to a directory which is the base of part of the original file path.

Clicking on a Focus segment shows focus session information and displays up the position vs HFR measurements from that session. Clicking on a Guider segment shows a drift plot from that session, (if it's guiding) and the session's RMS statistics. Other timelines show status information when clicked.


A variety of statistics can be displayed on the Stats graph. There are too many for all to be shown in a readable way, so select among them with the checkboxes. A reasonable way to start might be to use rms, snr (using the internal guider with SEP Multistar), and hfr (if you have auto-compute HFR in the FITS options). Experiment with others. The axis shown (0-5) is appropriate only for ra/dec error, drift, rms, pulses, and hfr. These may be y-axis scaled (awkwardly) using the mouse wheel, but the other graphs cannot be scaled. To reset y-axis zooming, right-click on the Stats plot. Clicking on the graph fills in the values of the displayed statistics. This graph is zoomed and panned horizontally in coordination with the timeline.

Ekos Tutorials


StellarMate is shipped with a VNC Server. This enables you to access the whole StellarMate desktop remotely. To connect to VNC, you can either use a Desktop/Mobile VNC Client, or simply via any browser.

The VNC address is: https://stellarmate_hostname:6080/vnc.html

Where stellarmate_hostname is the actual hostname (or IP address) of your unit and 6080 is the port. If you do not know the unit hostname, you can find the hostname in your StellarMate App.

You can use Real VNC which is available on all platforms to access stellarmate.

Once you access StellarMate, you can use it like any full-fledged computer. The default username is stellarmate and the default password is smate.