SH2-206 Time for a reset

Over the Christmas period, I had chance to spend a night under the clear sky that blessed Herefordshire for one whole night!  My chosen target was one from the Sharpless catalogue, SH2 206.  In 2025, I bought a new book called The Astrophotography Sky Atlas by Charles Bracken.  As the title suggests, it's a collection of astrophotography targets split into northern and southern hemisphere views and set out on straight forward star charts.  It's helped broaden my AP horizons significantly, pointing me in the direction of targets that I never new existed by reading any of my other books.  It's a catalogue of 312 emission nebulae strong in HII regions.  This means many of those targets, will show strong in red channels.

As exciting as it is to be let loose on a new catalogue, it's the basics of astrophotography that can often bring you back down with a thud.  This was one of those times, and this image is one of those ones that I do periodically that make me realise something is wrong or forgotten.  The primary reason for me having the observatory is to make everything as close to switch on and play as possible.  I don't need to use valuable imaging time setting up, getting polar aligned and star aligned for every session.  But even with all this convenience at the finger tips, sometimes, you just need to go back to the beginning.  Before I cover that though, the image...

This image of SH2-206 is the result of 122 98 second exposures, plus calibration frames, all stacked using the WBPP script in PixInsight and processed in the same software.  You can see by the amount of red in the image how much influence the HII has.

At first glance, this image is OK I guess.  Far from my best, but OK.  But I struggled to get much out of it, and to be honest I'm not entirely happy with it.  I can't explain why, but the final stacked but unprocessed image didn't feel right.  It was too late by that point, so I carried on anyway.  During the processing of the image while I was waiting for various things to happen, I started thinking what I needed to do.  Collect more data?  It's a fair shout.  Though it has somewhere in the region of 3 hours of data, there's not a lot to go at, so it must be pretty dim.  It's also quite small, so perhaps suited to a better, longer focal length rig.

What else could I do?  One of the other advantages of having the observatory, and a TEC controlled camera is that when it comes to calibration frames, because the orientation and focus of the camera doesn't really change between sessions, you can get away with taking a library of calibration frames, and use them for numerous imaging sessions because everything should in theory remain the same.  While looking through my calibration frames, I noticed that they were dated August 2025.  This meant that I actually took that library during the hottest Summer we have experienced in the UK for a long time.  Fine for the imaging work done that Summer, but there must be an impact by air and equipment temperatures in the imaging train between Summer and Winter temperatures.  That was my first revelation, a new library of calibration frames was needed before I next had a processing session.

Thinking further, since last Winter, every time I have been in and out the observatory, occasionally I have nudged the mount.  Nothing major, and very hard to avoid given the cramped nature in there.  I bet that the mount had been nudge to the extent that it effected polar alignment.  That was quickly added to the 'to do' list.  One other thing then came to mind.  In a somewhat unsuccessful imaging run over the course of an hour a week or so before, I noticed that after a meridian flip following the target I was imaging passed through the meridian, when it come to plate solving back on the target before resuming imaging, there was a discrepancy between where the mount said it was pointing, and where Cartes du Ciel said it was pointing.  Indeed, when I stretched one of the sub frames, it was clear that alignment was way off.  At that point, it was getting on so I sacked the imaging run off. It was time to also re-align the mount. 

The next opportunity under a clear sky I reserved my time for getting through all these things that I'd thought about.  Focus was also out a little bit, probably due to the thermal differences between seasons, so I also can that back on track using a bhatinov mask.  Then, a couple of days later under a clear daytime sky, I shot some new calibration flat frames with the roof open, before closing it and taking dark and flat dark frames too.

All in all a good lesson in not forgetting the basics, and that just because you have an observatory and permanent setup, you still need to do a bit of upkeep from time to time.  Now I just need to wait and see what difference these changes have made!