Celestial hemisphere:  Northern  ·  Constellation: Cygnus (Cyg)  ·  Contains:  Extremely wide field
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Equipment

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Acquisition details

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Description

I just kept taking 20 second subs every night that I could, until November 10th. I ended up with 5,500 subs, of which 5,089 were usable, giving me 96 panels for the mosaic which is now covering a much bigger portion of Cygnus. 

All panels taken after October 22nd (about 45) were horrible, actually blurring things instead of improving them. After some trial and error I realised it was the flats. For some reason, the 16 flats I took in October were adding an incredible amount of noise, despite correcting vingetting almost perfectly. So I spent two days trying to produce a really good master flat. It seems some reflections from nearbly light pollution manage sneak through from funny angles when I am imaging (despite the lens hood) so I was able to get either good vignetting correction or very nice detail preservation, but never both. I also have a small sensor tilt that complicates matters.

I settled for a set of 96 2-second flats carefully produced with a tablet fuzzed with a couple of A4 sheets, and 60 dark flats to get rid of the thermal stuff. (I also tried with 120 bias frames instead of dark flats, I could not see any difference in the master flat.). The first panel I did with the new master flat was about a million times better than the one with the old master flat. Still had some vignetting, and some uneven correction due to the sensor tilt, but they were both really easy to correct with APP's background removal. I also tried one of the older panels (the ones before October 22nd) and that too came out with serious improvements.

Therefore, the only way forward was to bit the bullet and recallibrate/reintegrate/redo background removal on all 5089 subs and 96 panels. That took 10 days, with the computer working constantly and me doing background extraction in parallel. 

Processing the integrated mosaic was actually quite easy since I had practised a lot with previous/partial versions in the past three months. A quick wipe/autodev/contrast enhancement/color correction/superstructure/noise removal in Start Tools followed by some finishing touches in Darktable. 

I also did a starless version with StarNet, purely to appreciate the nebulous structures that are somewhat obscured by the 30,000+ stars in the image.

Cygnus is an amazing constellation and totally expect to be visiting it again next year.

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Title: starless version

Description: This version is done with Starnet. It is not ideal but does make the nebulosity more pronounced.

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