I’m not talking about me here. Although, the title of the post can apply to my work life and personal life in light of covid-fatigue, this post is about focus on my telescope. My setup is mostly automated once the telescope is placed in position and polar aligned. I know, in one of my posts I mentioned vlogging about my setup for any new astronomers out there. I just have been too lazy to do it #COVIDfatigue. I’ll get to it at some point but not sure if it is worth anything for the 2 subscribers that I have 🙂 . So, where was I, oh yes, focus on my telescope. My setup is mostly automated and I used EKOS and Kstars for imaging. The software also has focusing algorithms if you have a motorised focuser. I have so far struggled with getting pinpoint star focus using the algorithms. In fact, I have wasted a couple of wonderful nights because the pictures were not quite in focus and the stacking software did not reconize the stars. Here is an example image from last night which was a lost cause. I was trying to capture a portion of the Markarian’s chain – a popular target for the galaxy season.
One of the challenges imaging from my driveway, is the limited time window objects are visible for. The field of view is limited with my house obstructing all of western part of the sky and the houses across from my house cover a substantial portion of the sky on the eastern side. The only saving grace is a park diagonally across from my street that allows for a better view of the south eastern sky. With this limited time window, it is imperative for me to get the polar alignment, focus and plate solving done quickly so that I can focus on capturing images. After letting the automated focus routine complete succesfully, I was pretty stoked to get these many galaxies in the FOV of my CCD. I started capturing 300 second images. When I looked at the captured subs, they looked fine. I mean the focus was not perfect (the stars were a bit bloated) but I thought it was possibly due to exposure time. After, what I thought was a succesful couple of hours of data gathering, I called it a night and tried to stack the images to see how they look prior to getting some darks. Stacking the images threw a warning that only 1 image would be stacked. Quick google search revealed that this usually happens when the image is not in focus 😐 . It was too late to redo focus and capture the images that night. So i called it quits and planned to set up the following night as well.
The following night I decided that I am not going to take any chances with focus. So after polar alignment, I slewed to a brightish star and placed a Bahtinov mask for focus. If I did not already mention, once I set up my gear, I sit at home and work on my computer for imaging while watching the live feed of my driveway from security cameras. So, using Bahtinov mask meant I either sit outside while focusing or do a couple of in and out trips. In anycase, I prefer automated focus to avoid either options!
After succesfully getting the camera in focus using the mask, I did plate solve and tried a different target – NGC 4645 Needle Galaxy. It was a fruitful night as I was able to capture this image. It has a bunch of pollution artifacts and I need to get a lot more exposures to get better Signal to Noise ratio but I am pleased with the results
With every failed/bust night, I learn something that I can put to use for the subsequent sessions making my process more and more efficient. However, I still need to do a bit of research on how to get pinpoint focus with the EKOS focus module algorithms rather than using Bahtinov mask. This will especially be useful if I set up a remote observatory at some point in the future. Hopefully, by next clear night, I will be able to figure the autofous routine and not need to use the Bahtinov mask!
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