analyzeThe 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.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 (eg. 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.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.


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.

Primary Telescope & Guide Telescopemount config

  • Aperture (mm): Specify the value of aperture for your telescope. Defaults to the values set for your telescope in your current running profile.
  • Focal Length (mm): Specify the value of focal length for your telescope. Defaults to the values set for your telescope in your current running profile.

Configurations: You can set up to 6 configurations for your mount module. To save the information, select an unused Config # from the drop-down menu and then enter a name in the field next to it, then click on Save Telescope Info.

 It is recommended to specify the primary & guide telescopes in the Ekos Profile as this ensures the correct information is always used for this profile regardless of the INDI driver state.


This group shows the following values of your mount:mount coords

  • RA: Right Ascension
  • DEC: Declination
  • AZ: Azimuth
  • ALT: Altitude
  • HA: Hour Angle
  • LST: Local Sidereal time

Meridian Flip

You can do a Meridian Flip from the Mount Module.

Equatorial mounts flip after crossing the meridian in order to prevent the imaging equipment train from hitting the tripod. With Ekos, you can set an hour angle limit which if exceeded, the mount will be commnded to flip. The mount must begin tracking east of the meridian in order to the meridian flip to be commanded in Ekos.

When commanding a meridian flip, Ekos will suspend the autoguiding process and waits until the mount completes the flip. Once the mount begins tracking again post meridian flip, Ekos will plate-solve and make any necessary slew commands to bring the mount to the exact location it was tracking prior to the flip.

Next, it will automatically capture a frame and select a suitable guide star, performs calibration, and resumes autoguiding. If In-Sequence focuing is enabled, it will also capture and focus a suitable star. It then resumes the capture process form where it left.

All these steps are completely automated and require no user intervention! 

So just set when you want the meridian flip to occur at the mount module. Remember that the setting is in Hour Angle (HA). 1 HA = 15 degrees, therefore 0.1 HA = 1.5 degrees West of the Meridian. 
Always use a positive value to ensure proper meridian flip takes place. Using zero could theoretically work but it is at the very edge where the decision to flip or not is made by the mount, so it's safer to use a slightly higher value like 0.1 HA.
Controls brief descriptionmount meridian flip
  • Flip if HA >: Request a meridian flip if the hour angle exceeds the specified value. Capture and Guiding will be suspended and resumed after the flip is complete.
  • Hours: Set Hour Angle unit to Hours
  • Degrees: Set Hour Angle unit to Degrees. If the mount is configured to flip at 5 degrees, set the value in Ekos to 3 degrees less (2 degrees).
  • Pier Side: Shows the pier side direction.

mount reset

  •  Clear Model: Deletes all mount alignment points.
  •  Clear Parking: Clears parking information.
  •  Purge all configuration: Deletes all the configuration files (config #1, config #2, etc)

Auto Park

This feature Auto Parks your mount at a specific time and you can choose if you want to park it everyday or not. To start the Auto Parking process, click on the Start button.mount meridian flip

  • Park At: Specify the time when you would to park your mount.
  • Everyday: If you want to park your mount everyday at a specific time, then check this checkbox.
  • Timer: Displays the countdown until the mount is parked. To activate the countdown, click on the Start button.mount rightpane
  • Start : Starts the Auto Parking process.
  • Stop : Stops the Auto Parking process.

Auto Parking should not be used when scheduler is active as it can interfere with the scheduler operation.

 Mount Control: Opens up the Mount Control dialog. This control is also accessible from KStars toolbar.

Tracking: You can enable or disable tracking from the mount module.

Parking: You can park or unpark your mount from the mount module.

Limits: You enable Altitude Limits or Hour Angle Limits if you do not wish your mount to move past a specific limit. The values are expressed in hours. Setting a 1 hour (HA) limit means your mount is restricted to 15 degrees east and west of the meridian. Setting it to 3 HA (3*15) means your mount is free to move 45 degrees east and west of the meridian.

Mount Controlmount control

Clicking on this button will open the Mount Control dialog where you will be able to control your Mount manually using arrow buttons and abort movement using a STOP button. It is possible to reverse the controls if you feel it is easier that way to control your mount. The speed of the mount can be controlled using a slider which has four speeds: Guide, Centering, Find, and Max. The details of the mount's position are shown, which are: RA, DEC, AZ, ALT, HA, and ZA. You can specify the target you want to move to using the Target field. To specify a Target, click on the magnifier icon  and selecting an object. You can specify manually where to go to by filling the RA/AZ or DE/AL field and then choosing the type by clicking on the appropriate setting. There is a status bar that shows if the mount is idle or doing some action. The small button on the bottom-right corner is used to sync the GPS location. There are four main options for automatic mount control:

  • GOTO: Slews your mount to the selected target and tracks it.
  • SYNC: Sets the mount coordinates as the current coordinates. No motion takes place.
  • PARK: Park the mount to its parking position. The parking position varies from mount to mount. Some driver support custom parking positions while others support only one static parking position. For GEM mount, parking position is usually with the mount looking toward the celestial pole with the counter weights down.
  • UNPARK: Unparks the mount so it can be moved.

ekos scheduler


Ekos Scheduler is an indispensable arsenal in building your roboic 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 utlized 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 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 Now, 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 observeration, 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
  • Unparkig 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 Aquisition

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

  • 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 earilar version of the scheduler, but the basic principles still apply today:

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

Aborted Job Management

Define what should happen when a job steps into an error or aborts:

  • Don't re-schedule (None): Don't restart the job in case of an error or an abort.
  • Re-schedule after all terminated (Queue): If a job gets aborted, the scheduler will only re-schedule it if when all jobs are finished or aborted. If this is the case, the scheduler re-schedules all aborted jobs and sleeps for the given delay.
  • Re-schedule immediately (Immediate): As soon as a job gets aborted, the scheduler will re-schedule it and waits the given delay.

If the option for re-scheduling errors is selected, errors are handled like aborts. Otherwise, jobs that step into an error are never re-scheduled.

Startup & Shutdown Scripts

Due to the uniqueness of each observatory, Ekos enables the user to select startup and shutdown scripts. The scripts takes 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 as 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 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 KDE notifications, the user can configure audible alarms and email notifications for the various events in the scheduler.

Manual Target Selection

When selecting a target usign the Ekos Find Tool, the objects equatorial coordinates (J2000) are automatically filled in the RA/DE fields. You can also define your own custom target. Simply type in your target name in the target field and then manually enter the desired J2000 coordinates in the respective fields.

KStars provides a conventient method to Copy Coordinates. Simply right-click on the desired object or point in the sky where you want to image, and click copy coordinates. You can paste the coordinates in any text editor and then copy back the J2000 coordinates in the scheduler RA and DE fields as shown below.

scheduler manula target

Mosaic Wizard

mosaic wizardHubble-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 to 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. Start the Mosaic Job Creator by clicking on the icon next to the Find button in Ekos Module.

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 to your desired target then use the Align module to solve the image and obtain the position angle.


Next, enter the desired number of horizontal and vertical panels (e.g. 2x2, 3x3...etc) and then click Update. The target FOV shall be calculated given the number of panels and your camera's FOV and the mosaic overlap shall be displayed. By default, the percentage of the overlap among images is 5%, but you can change this value to your desired value. You can also move the complete mosaic structure around to fine tune the position of the mosaic panels. When satisfied, click Create Jobs and 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. Before starting the Mosaic Job Creator, 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.

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


The observatory module is used to manage the dome and weather-triggered shutdown procedure. It has weather data directly displayed in the module. Along with the configurable thresholds for Warning and Alert states, you can rest easily knowing that KStars can take the appropriate actions to protect your observatory from adverse weather conditions. The observatory module also includes a dedicated weather widget with love plotting for each parameter.



  • Position: Controls the position of the Dome.observatory dome
    • Motion: You can move the Dome in four ways.
      • Absolute: Select the absolute position you want the Dome to move and then click on Move (abs). This will move the Dome to the absolute position you set.
      • Relative: Select the amount of degrees (either positive or negative) you want the Dome to move from the current position and then click on Move (rel). This will move the Dome to the relative position you set.
      • Clockwise (CW): Rotates the Dome Clockwise forever until you click on Abort.
      • Counter Clockwise (CCW): Rotates the Dome Clockwise forever until you click on Abort.
  • Slaving: If enabled, Dome motion will follow telescope motion.
  • Park/Unpark: Park or Unpark the Dome. For advanced control, please use the INDI Control Panel.
  • Abort: Aborts the Dome motion.

Shutterobservatory shutter

  • Open/Close: You can open or close your shutter through the observatory module.

Observatory Status

  • Dome: If selected, the dome needs to be unparked for the observatory status being "READY".observatory status
  • Shutter: If selected, the shutter needs to be open for the observatory status being "READY".
  • Weather: If selected, the weather needs to be OK for the observatory status being "READY".
  • Ready: Observatory status. Select the observatory elements that are relevant for the status:
    • Dome: unparked → ready
    • Shutter: open → ready
    • Weather: OK → ready

Weatherobservatory weather widget

Current data of the weather sensors. Click on the sensor name to display its data over time.

  • auto scale values: Scale the value axis to the current value range.
  • trash canClear sensor data history.
  • Graph: You can see the values of both axes if you hover over the graph. You can zoom in or out using the scroll wheel.


  • Alert: Check this checkbox in order to get an Alert whenever any weather value goes under or above the range set in your weather driver INDI Control Panel.
    • Park Dome: Parks the dome whenever you get an alert.observatory actions
    • Close Shutter: Closes the shutter whenever you get an alert.
    • Status: Shows the status of the alert.
    • Delay (sec): Delays the alert after n amount of seconds.
  • Warning: Check this checkbox in order to get an Warning whenever any weather value is close to going under or above the range set in your weather driver INDI Control Panel.
    • Park Dome: Parks the dome whenever you get a warning.
    • Close Shutter: Closes the shutter whenever you get a warning.
    • Status: Shows the status of the warning.
    • Delay (sec): Delays the warning after n amount of seconds.


ekos astrometry

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 StellarSolver library. Ekos begins by capturing an image of a starfield, feeding that image to the 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 Assitant Tool: An easy to use tool for measuring and correcting 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 built-in StellarSolver, or remote solver

  • StellarSolver: The default solver in Ekos. StellarSolver supports native plate-solving based on Furthermore, it supports online (internet-based) solving, ASTAP, and local offline solver (Available for macOS & Linux). The built-in solver is fast and supported across all platforms.
  • 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.

StellarSolver Integrationekos astrometry

StellarSolver is an astrometric plate-solving library that has been integrated into Ekos in order to provide accurate and efficient offline plate solving.

For plate-solving there are several parts in StellarSolver that are important:

Source Extraction

To find the stars in your image in order to solve. In StellarSolver, there are options for 3 different methods:

  • Internal SEP: this requires no external programs, it is the same SEP star extraction algorithm that has existed in KStars for Focus and Guiding for awhile noSource Extractionw. It is essentially a library version of the method below (though there are some differences which is why they give slightly different results). It is entirely internal to the program, so there are no files saved to disk for the extraction which is great for Raspberry Pis etc.
  • External Sextractor: this does require an external program, SExtractor, or the Source Extractor. This is their official standalone program. The drawback is you would need to have sextractor installed and it does save a bunch of files to disk in order to do its operations.
  • BuiltIn Sextractor: This uses whatever method of source extraction the solver uses by default. StellarSolver uses SEP, just like the Internal SEP setting. Local uses its own source extraction method which uses a bunch of external resources including python, netpbm and other packages. And finally, ASTAP has its own internal source extractor which is pretty good.

Note: Either Internal SEP or External Sextractor should be superior to the built-in version of the programs. SExtractor is very good at extracting stars, and that greatly speeds up solving, but it requires tuning up the options to perfect it for your optical train.

The Solver

The program that will be used to do the solving of the sources that were found. In StellarSolver, there are 4 options for that

  • StellarSolver: This option uses an internal library build of It uses no external files like configuration files etc, and saves no files to disk (except 0KB solved and cancel files) which is great forsolving method Raspberry Pis. Since this library is entirely internal, no programs have to be installed beyond KStars itself, so if you are going to use this option, you don't need the package at all. This is going to make a world of difference for Windows users who cannot install unless they do it in a compatibility layer.
  • Local This option uses the good old fashioned local installation many users have used with KStars for years. The only differences in Stellarsolver are that we no longer need the configuration files, we can do parallelization to make it MUCH faster, and we can use Internal SEP or External Sextractor to give it the sources to solve.
  • Local ASTAP: ASTAP was available in KStars previously, but more options have been implemented for using it in StellarSolver as well as giving you the option to use Internal SEP or SExtractor with it. The options for ASTAP are now shared with astrometry so you can just set your options in the profile and it will work fine. ASTAP does NOT support parallelization.
  • Online This option was previously available in KStars as well, but a bunch of work has been done on it to make it work better, to use Internal SEP or Sextractor if you like, to use the options in the profiles, and to provide clearer feedback to the user about what is going on. Technically, online is already using parallelization on their server, so there was no need to implement parallelization for it.

The Options Profiles

Here are the profiles that have been developed:

Profiles mainly for Solving:
1-FastSolving: solve images fast, but it does not do parallel solves.
2-ParallelSolving: It can be faster than FastSolving, but does not work nearly as well as the next 2.
3-ParalleLargeScale: This profile is meant to solve DSLR scale images very fast. It assumes larger image scales to solve faster than the above.
4-ParallelSmallScale: The DEFAULT for solving. This profile is meant to solve telescopic images quickly. Most users should probably use this one.

Profiles mainly for Source Extraction in Focus and Guide
5-AllStars: This profile is meant to detect all the stars in an image.
6-SmallSizedStars: detects smaller stars and ignores bigger stars
7-MidSizedStars: detects medium-sized stars
8-BigSizedStars: detects bigger stars and ignores smaller stars

ANSVR Solver

Users on Windows OS can install ANSVR Local solver and use it as a pseudo online solver that happens to be running a server on their machine. It is not recommended given that StellarSolver is built-in and faster. It is left in the documentation for users who want to try it out.


ANSVR mimics the online server services on your local computer; thus the internet not required for any astrometry queries. From the point of view of Ekos, it is still communicating with an online server.

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:

astrometry windows ansvr

Do not forget to include the full URL including the HTTP part. 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 Therefore, if you would like to use StellarMate remotely to solve your images, simply change the 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.

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 indexes settings

Automatic download is only available for Ekos users on Linux & macOS. 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 following:

  • Required Required
  • Recommended Recommended
  • Optional 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. By default, StellarMate comes pre-installed with index files 4206 to 4219. Due to size restrictions, indexes 4204 and 4205 are not included in the official StellarMate OS image. It is recommended to download them. From Astrometry Index Files tab, click on Index File Location combo and select the first entry below All Sources. Once selected, you should be able to download the necessary index files as illustrated below.

Screenshot 20210817 125445

Please only download one file at a time, especially for larger files. Once you installed all the required files, you can begin using the offline 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.

Index FilenameFOV (arcminutes)Debian Package
index-4219.fits 1400 - 2000 astrometry-data-4208-4219
index-4218.fits 1000 - 1400
index-4217.fits 680 - 1000
index-4216.fits 480 - 680
index-4215.fits 340 - 480
index-4214.fits 240 - 340
index-4213.fits 170 - 240
index-4212.fits 120 - 170
index-4211.fits 85 - 120
index-4210.fits 60 - 85
index-4209.fits 42 - 60
index-4208.fits 30 - 42
index-4207-*.fits 22 - 30 astrometry-data-4207
index-4206-*.fits 16 - 22 astrometry-data-4206
index-4205-*.fits 11 - 16 astrometry-data-4205
index-4204-*.fits 8 - 11 astrometry-data-4204
index-4203-*.fits 5.6 - 8.0 astrometry-data-4203
index-4202-*.fits 4.0 - 5.6 astrometry-data-4202
index-4201-*.fits 2.8 - 4.0 astrometry-data-4201-1
index-4200-*.fits 2.0 - 2.8 astrometry-data-4200-1

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. Initial 2-3 star alignment might be required depending on your mount make:

  • EQMod, Celestron Aux (e.g. Evolution), AstroTrac: No need to perform initial alignment, Ekos alignment module can work with the mount right away after power up given the mount is in its home position.
  • All other Mount drivers: Must intially perform 2-3 star alignment using the handset before you can use the Ekos alignment module.

Ekos Alignment module features the following functions:

  • 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.

Warning! 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 celetial pole before solving the first image. Solving very close to the poles will make your mount pointing worse so avoid it.

Alignment Settingsastrometry settings

Before you begin the alignment process, select the desired CCD & Telescope. You can explore options that are passed to the 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 actual solved coo
  • 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 solver. Click the Edit button to explore the options in detail.
  • Solver: Select solver type (Online, Offline, Remote). 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. Settings

Options for offline and online solvers.

stellarsolver options

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

  • Use Sextractor not python: This allows you to use Sextractor to make XY Lists in order to avoid using python with It vastly improves the solver speed. This is a good option to be enabled on macOS since they don't need to install python.
  • Rotator: Rotator threshold in arc-minutes when using Load & Slew. If the difference between measured position angle and FITS position angle is below this value, the Load & Slew operation is considered successful.
  • Time out: Timeout in seconds to wait for astrometry solver to complete.
  • 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 recommeneded to keep this option on.
  • Overlay: Overlay captured images unto the sky map of KStars.
  • Upload JPG: When using online, upload all images are JPEGs to save bandwidth as FITS images can be large.
  • Auto Park: Automatically park the mount after completing Polar Alignment Assistant Tools.

Warning: Turning Auto Park off might lead to inaccurate results.

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.

Imaging Options

  • Use Scale: Set image scale to speed up solver as it does not have to search index files of different image scales.
    • Low: The lower end of the imager scale, calculated as a little smaller than the shorter dimension of the image.
    • High: The high end of the imager scale, calculated as a little bigger than the longer dimension of the image.imaging options
    • Units: The units of the imager scale bounds above.
      • dw: degree width
      • aw: arcminute width
      • app: arcsecs per pixel
    • : Update Image Scale Bounds from the currently active camera and telescope combination.
  • Auto Update: Automatically update image scale values when CCD and/or Mount parameters are updated.
  • Down Sample: Downsample the image to shrink its size and speed up the solver.
    • Auto: Automatically determine downsample value based on image size

Position Options

  • Use differential slewing instead of syncing: Do not use Sync when Slew to Target is selected. Use differential slewing to correct for discrepancies. This is useful on some mounts (e.g. Paramount).
  • Use position: Set estimated position to speed up astrometry solver as it does not have to search in other areas of the sky.
    • RA: The RA of the Estimated Telescope/Image Field Position in hh:mm:ss notationposition options
    • DEC: The DEC of the Estimated Telescope/Image Field Position in dd:mm:ss notation
    • Radius: The Search Radius for the Estimated Telescope/Image Field Position in degrees.
    • : Update coordinates to the current telescope position.
  • Auto Update: Automatically update position coordinates when mount completes slewing.
  • Custom: Additional optional options.

If solving always fail even though the image contains lots of focused stars, then it is likely that either the frame field of view (FOV) and/or mount position is wrong. Turn off Use Scale or Use Position then try solving again. If the solving succeeds then that confirms that either the FOV scale or position are indeed incorrect.

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.


Sometimes, the solver would fail to solve an image for various reasons. Here are some tips to get you started in the right direction:

  • Do you have the correct index files installed for your FOV? By default StellarMate come preinstalled with index files 4206 to 4219, but if your FOV is on the narrower scale, you might need to install more index files.
  • Do the RA/DE coordinates of the telescope in Alignment Module make sense? By default, the solver searches within 30 degrees of the current mount location. If the mount is way off in the sky, the solver would fail. If this happens, go back to your parking home position and then slew to a nearby star. If the star is off by more than 30 degrees, then there is something wrong with the mount, time, and location settings so check each of those.
  • Check the quality of your image, does it have suffcient stars? can work with minimal data, but if there is a lot of noise and very few stars, it might struggles to find a solution. Try increasing exposure time to compensate.
  • Increase binning to the maximum supported by your camera.
  • Increase exposure time to 10 seconds or more.
  • Enable Dark Frame option to clean up the image before sending it to the solver.
  • Perform rough Polar Alignment before using the alignment module.
  • Automatic downsampling is turned on by default. It essentially reduces the size of your image before it is fed to the solver. For most users, this option improves solver efficiency. However, it can create issues for others. Go to Astrometry options and turn off automatic downsampling and if that doesn't work, try turning off downsampling completely.

Polar Alignment

Polar Alignment Assitant

When setting up a German Equatorial Mount (GEM) for imaging, a critical aspect of capturing long-exposure images is to ensure a 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 stars 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.

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 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.


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 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.

polar align nearby 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 align start

Firstly, you select the direction of rotation, degrees of rotation, mount speed, and toggle manual slew. After the first capture If manual slew is disabled, the mount rotates automatically and captures the three required images by the previously selected settings.

If manual slew is enabled, the user has to move the mount by about 30 degrees after each image when prompted and click next to capture the new image. Doing so until 3 images have been captured.

polar align manual rotate

Since the mount's true RA/DE are resolved by astrometry, Polar Alignment Assistant constructs 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.Since the mount's true RA/DE are resolved by astrometry, Polar Alignment Assistant constructs 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.

polar alignment select star

 Next, refresh the camera feed by setting the refresh rate and clicking "Refresh" 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 align horizontal center

polar align select refresh

If you are away from StellarMate or PC, you can use your Tablet to monitor the camera feed while making corrections Using the StellarMate app.

polar align stellarmate app

Alternatively, you can 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.

Legacy Polar Alignment Workflow

Using the Polar Alignment mode, Ekos can measure and correct for polar alignment errors. To measure Azimuth error, point your mount to a star close to the meridian. If you live in the northerm 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 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 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) 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.