A quick and dirty monochrome image from our last night of reasonable sky as high pressure scoots away from UK - interrupted by high cloud and ground mist. I had hoped to frame both NGC 7635 and M52, which looked possible using a FOV calculator [
http://www.12dstring.me.uk/fovcalc.php].
My DSI Pro, 8" SCT with f3.3 reducer, gives a predicted field of view of 45 x 34'. Plate solving my image has a FOV of 38 x 29' [
http://nova.astrometry.net], presumably due to the extra distance from the sensor, due to the infamous Meade filter slide, which increases distance to the sensor by about 12mm.
I don't have a filter wheel, so the slide does provide a means of changing filters relatively easily, albeit rather clunky, prone to dewing and light ingress. I came across this 3D design by Masayki Asai - individual filter slides that are easy to change, keep dry and sealed [
https://www.thingiverse.com/thing:3287902]. Even better my brother in law, George generously offered to print these for me, for which I am very grateful.
So, here it is, warts n' all, just over an hour of data, after a rough Polarscope alignment. My autoguider did a good job of tracking at 1" but struggled with field rotation high at the zenith. Nebulosity did an even better job of aligning (translation, rotation and scale) and stacking the 5m subs, and Startools helped reduce or at least hide the significant noise that resulted.
In astrophotography, 'almost' is not good enough, there are so many variables, especially with a manual setup, that very often it seems to be as much luck as judgement.
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