EKOS

Using EKOS to capture the Wizard Nebula (NGC7380) on the Mac

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This will be a general walkthrough of a typical capture session with my AstroTech AT6RC setup.

This should be a good walkthrough for someone not familiar with the system to enable capturing their own images. However, I'm not covering equipment setup in this post, but might cover it in the future in another post.

A few caveats with my particular setup. I break it down and set it up each night, so I require a new polar alignment before each session. My AVX mount doesn't fully support the park function in EKOS, so after a nights session, I cannot auto park, but others may have a mount that supports this feature.

Connect your equipment

The first step in my process is to set up all my equipment, connect it to the Mac laptop and start with an All Star Polar Alignment (I can't see Polaris, so use this method built into Celestron mounts). After this procedure is complete, I load up Kstars, then press the EKOS button on the top bar to launch the EKOS capture system. I then press the connect button to connect to my equipment which I have pre-setup within EKOS prior to this nights session.

Focus Module

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The mount is probably already aimed at your last alignment star from your polar alignment, and this is typically good enough to use for focusing. I select the Focus Module and then press the capture button. This grabs a single screen and displays it in the screen preview window. Since I have a motorized Moonlite focuser, I can select a star with the cursor (it puts a green box around it in the screen), and then press the Auto Focus button. This begins the auto focus routine where it begins automatically focusing in and out and measuring it's effects on FWHM (Full-Width Half-Maximum) which continually measures the width of the star to get it as small as possible after iterating multiple times. Now, we're in focus, and can move on to the next step. (Side note, if you don't have an automated focusing system, you can use the camera module's live preview feature and a Bahtinov mask to focus instead of using this module.)

Mount Control Window

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The next part of the process is to open up the Mount Control module, and select "Mount Control" in the upper right of the window. This will open a small control pad with arrows, and a target search to move your mount. I'll press the search icon and type in a target name for a simple, easy to identify target for plate solving. Usually I pick an open star cluster for this process. I selected NGC129, then pressed the GOTO button to slew the mount to that target.

Alignment Module

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Now that I have slewed to NGC129, I press the Alignment Module tab to go through a plate solving process to improve my GOTO model inside the mount and EKOS module. The reason you want to do this is both so that you have increased slewing accuracy, and so that once you pick your target and slew to it, you have confirmation that this is in fact the target you picked. Additionally, this helps with the meridian flip and ensuring that once the mount has flipped, after passing the meridian line, that your target is picked up in the exact same spot it left off before the flip. 

Usually what I do in this first step is select Sync under Solver Action. Then I press Capture and Solve. All I'm doing here is plate solving the current position to tell the mount exactly where it's aimed. I had told it to aim at NGC129, but after this first solve, it shows the mount is way off. Not knowing for sure if this is an adequate target, I pick a new one using the Telescope Control and aim at M39, an open cluster. I once again set it to Sync, and press Capture and Solve. Now I'm fairly close to the target, but not quite in the green area. I press goto one more time now that my mount knows where it is, and then Capture Solve/Sync one more time and see if the last slew was closer to the target. Finally, we're in the green and good to go to our final imaging target for the night. I pick the Wizard Nebula NGC7380, and press goto. Once there, I perform a Capture and Solve/Move to target. This will perform multiple Capture and Solve routines moving the mount each time getting the target lined up perfectly. Once it's good the Capture and Solve process stops. Time to turn on guiding now.

The Guide Module

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With our target picked, and GOTO plate solved to the target, we're ready to start guiding. This process is fairly straight forward. Dithering is turned on by default (you can check it by going to the options button in the lower right corner of the window). Now, we press capture, this shows you a single image from your guide cam. Select a star with your mouse, and it highlights with a green box. Press Guide, and the guiding calibration begins. This process is automatic, and you can watch the steps it's performing in the text window at the bottom of the screen. Once it's complete, guiding starts automatically. Now it's time to program our image sequence and start capturing.

The Sequence Module

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This is the final step for my process for an evening capture session. For the Wizard Nebula, I had planned on capturing it in bi-color over a two night period. Tonight is the first night, so I only plan to capture 7-8 hours of HA (Hydrogen Alpha filter), basically as long as I can before the sun comes up. Tomorrow night, I'll be capturing OIII (Oxygen III filter) for another 7-8 hours using the same routine. Since I have a cooled camera, the first thing I do here is set it's temperature to -15°C, and press the set button. The temperature quickly begins to lower. I can check that box next to the temperature, and the sequence will not start until the temperature has been reached. Next I plug in my Exposure time, I've set it to 180s, or 3 min images. A count of 240, which is more than enough to cover me to sun up. I make sure the type is set to "Light" for light frames (as opposed to dark, bias, or flat). I set the filter to H-a, then under file settings I name the files with a prefix, in this case NGC7380, and I check off Filter, Duration, and TS (Time Stamp) so that those are appended to the file names that I'm capturing.

Now I've set all the perimeters for my sequence. I now add the parameters to the sequence que by going up to the top and pressing the "+" button. This adds it to the right into the que.  If I lived in a dark area, and wanted to capture more than HA during the evening, I could change my parameters and add sequences for OIII, SII, or LRGB and just make sure that I only put enough time into each so that the sequence can finish by the end of the night. But since I'm in a light polluted area, I need as much time as I can spend on each filter, so I typically spend one evening per filter and get decent imaging results.

We're done now with setting the sequence, and we're ready to run it for the evening. You'll press the play button at the bottom of the sequence window, and your camera will start capturing images until the sequence is complete. You can now tab over to the main window and watch the images roll in for the evening, or head to bed like I do, ready to wake up by sunrise and take down all the equipment before it gets too hot outside. (I live in the south where it's quite warm during the day).

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From here you can monitor the images that are being captured for the sequence you've plugged into the sequence editor.

Below is the final processed image from two nights of imaging. I processed it with Astro Pixel Processor, PixInsight, and Photoshop on my iMac Pro workstation. Full equipment details can be found at Astrobin.

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An Overview of EKOS Astrophotography Suite on the Mac

This is the main EKOS window. On the left are tabs that represent different sections of the application.

This is the main EKOS window. On the left are tabs that represent different sections of the application.

EKOS is the capture suite that comes as part of the KStars Observatory software package. It's a free, fully automated suite for capturing on Mac, Linux, and PC. It's not to dissimilar to Sequence Guider Pro on the PC. While the capture suite comes with KStars, you're not limited to using KStars. EKOS will also allow you to send commands to your mount from SkySafari on the Mac as well.

I'll break down it's use and capabilities screen by screen.

Main Window

In the main window shown above, you see tabs that represent each part of the application which include the Scheduler, Mount Control, Capture Module, Alignment Module, Focus Module, and Guide Module. From the main window you will see the currently taken image, the seconds remaining in the next image, as well as which image number you are on during the sequence, and the percent complete of the entire sequence with hours, minutes, and second remaining in your sequence. Additionally to the right of your image, you see your target and tracking status, focus status, and guiding status.

Scheduler

This is the Scheduler window, where you can pick your targets, and assign capturing sequences to them.

This is the Scheduler window, where you can pick your targets, and assign capturing sequences to them.

From the Scheduler, you can pick your targets, and assign them capture sequences (which are set up in the imaging module). Additionally there are some overall parameters you can set here for starting a session and ending a session. If you have a permanent observatory, you do things here like open and close your observatory with startup and shut down sequences, or set parameters for when to run your schedule based on the twilight hour, weather, or phase of the moon. The scheduler lets you set up multiple imaging sessions, mosaics, and more. And as the twilight hour approaches, it will start up and pickup imaging based off of priorities you set, or object priorities based on their visibility in the night sky. Imaging sessions can be set for a single night, or can be taken over multiple nights if it wasn't able to complete them in a single night.

Mount Control

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Mount control is fairly straight forward. This window shows the current aperture and focal length of your selected equipment. You can save multiple equipment configurations from this window for various telescope and guide scope combinations that you might have. Current tracking information is also shown in this window. If you select Mount Control in the upper right of the screen, it pops up a floating window with arrow buttons, speed and goto functions for manually controlling the mount. You can search for a target, and manually go to an object in the sky to start an imaging session without setting one up in the scheduler.

Capture Module

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From here you control all aspects of your imaging camera including setting up imaging sequences. For instance, I might have 7 hours of night time to image before the sun rises. I can divide that time up between each filter, and save the sequence of 120 captures, at 60s each at -20°C for each individual filter, and save that as a sequence which I can later load and reuse anytime I want to run that session during a 7 hour window. Or I could say I want 20 hours total on an object, and set all parameters for each filter to accommodate a 20 hour session, and save it. Or maybe I want one session for LRGB, and one for narrowband imaging. You can also set flat, dark and bias sequences. Flats have an awesome automatic mode, where you can set a pre-determined ADU value, and it will expose each filter automatically to the same ADU and capture all your flats in a single automatic session. It also supports hardware like the FlipFlat so that flat sessions can be run immediately following a nights imaging session. Additionally you can set guiding and focus limits for imaging sessions, and control when your meridian flip occurs.

Focus Module

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Here you can control all focus functions if you have a computer controlled focuser. I highly recommend getting one of these. Focusing can be set up to run automatically. It will capture a single image, and auto select a star, then run a sequence where it continues to capture, while moving the focuser in and out. Each time it is graphing the HFR on a curve plot trying to find the best point of focus. Depending on seeing conditions, it can get focusing down in 3-4 iterations, or sometimes 20. All parameters including threshold and tolerance settings for focusing are controlled in this window.

Alignment Module

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From this window you can polar align (assuming you can see Polaris), and also plate solve to locate an object center window or improve GOTO accuracy. Since I can't see Polaris from my location, I have to use my mounts built in All Star Polar Alignment process, then I can come to this window to capture & solve a target to improve it's GOTO accuracy. There are several nice features accessible here. You can load a fits file from a previous imaging session, it will plate solve the image, then move your telescope to that precise point to continue an imaging session. Or you can select targets from the floating mount control window, then capture and solve, or capture and slew to bring the mount as close to center of the target as possible. EKOS automatically uses this function during an imaging session to initially align to a target, and then realign once the meridian flip occurs.

Guide Module

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The guide module handles all guiding through your guide scope and camera. Press capture in the upper left, and hit guide, a star will be automatically selected, calibration starts, and once calibrated guiding begins. Additionally options can be set for dithering, and guide rate. For people who prefer PHD2, EKOS integrates seamlessly with it, and even shows PHD2's guiding graphs within the app and on your overview tab. I've not personally had any issues using the EKOS guiding, and it has an additional benefit of being able to reacquire a guide star after clouds interrupt your imaging session, and can continue the imaging session when it's clear again.

Overall thoughts

As someone who images regularly, and doesn't have a permanent setup (like an observatory), I like how much of the application can automate my nights imaging sessions. There is little else available on the Mac that is this full featured. The Cloudmakers suite comes in a close second for me, but is initially easier to set up and use. Additionally TheSkyX is also a full featured suite, however I've not used it. The setup process with EKOS isn't too difficult once you get an understanding of how the modules interact with each other and what all the options do. I hope this brief overview gives you enough of an idea that you can setup and use the software on your own. EKOS has a healthy number of contributors on the project, and regularly sees updates on a  monthly basis, and has good support through it's user forums.

The final image of M101 taken during this session that I captured the above screens from. This was actually 17 hours done over three imaging sessions.

The final image of M101 taken during this session that I captured the above screens from. This was actually 17 hours done over three imaging sessions.