Gamma Cygni Nebula (Sadr Region)

 09/06/23 -- first astrophotography session of 2023...fairly sad.  Utilizing the venerable Orion ST80, Hotech SCA field flattener and the ebay / generic dual band Ha / OIII filter, the Ha-modded Canon T3I on the CGEM DX mount to obtain some deep sky narrow band of an object not collected previously (oddly) -- the Sadr Region centered on Gamma Cygni.  Surprisingly clear skies (for once) coupled with a huge moon motivated a search for deep sky nebula suitable for narrow band, wide field imaging.  

Forgot to change the Astronomik EOS filter in the T3I...left the CLS filter installed instead of swapping out for the clear filter...resulting in challenges later in color balance.

Collection began on 09/05 with 109x100s light frames (total) and was followed up in the AM with flat frames and flat darks.  Of these only frames 003 through likely 083 are guided / good frames.

Analysis plot from that session shows results from collection and dithering with nominal RMS and SNR guide metrics across the evening (one second exposure with one second delay).  Guided collection stopped at approximately 02:23 with an a loss of guiding. This loss likely coincided with moon rise.  Dramatically poorer SNR is highlighted after moon rise... and oddly guiding does not restart.  Note -- collection of (unguided) frames continued until approximately 03:30...and so there are likely unusable frames towards the end of the session.

Indi / Ekos Analysis plots from the 09/05/2023 session with 109x100s light frames collected.

The Indi Allsky camera keogram (and timelapse video) was useful in understanding the likely cause of the loss of guide at about 02:30.

Indi Allsky Keogram from the evening / morning of 09/05/2023 showing moon rise at 02:30.

Collection continued this evening (09/06) with the mount left in place.  After double checking focus on guide scope (Cosmicar 50mm F1.8) and the ST80, brought up PHD2 over a compressed SSH link from the Odroid XU4.  This showed remarkable polar alignment with an error (after several minutes of guiding) of under a third of an arcsecond.

PHD2 drift alignment showing polar alignment error of 0.3 arc second

Meteoblue weather forecast for 09/06/2023

Clearbluesky weather forecast for 09/06/2023

Clearoutside forecast for 09/06/2023

Initial indi-allsky camera measurements at 21:21 on 09/21 showed reasonably good skies with a pseudo sky quality around 5000.

Indy Allsky camera (SVBony SV305 with Kodak C-mount 8mm lens) at 21:21 on 09/06/2023.

Initial frame solve and guide calibration was successful and early guide results showed RMS errors of ~1 arc second total.

Indi / Ekos Guide screen on 21:24 on 09/06/2023 showing initial guide errors of ~1 arc second.

Ultimately, 92 light frames were collected with capture running until 01:17am when interrupted by clouds or other disturbance.

Indi Allsky Keogram from the evening of 09/06/2023.

Results from AstroPixelProcessor from a final set of 107x100s light frames from 09/05 and 09/06/2023, 30 dark, 30 bias, 30 flat and 30 dark-flat frames.  

Sadr Region (Gamma Cygni Nebula) from 283 minutes (4.7 hours) of integration.

09/15/23  -- A third night of collection.  Fixed the Astronomik filter...replaced the CLS filter with a clear EOS filter.  No moon. Clear skies.  After checking focus for guide scope and the main OTA, established a polar alignment error down to ~3 arc seconds.  Set up collection for 180s x 40.

Clearoutside forecast for 09/15/23 from ~10pm.

Indi Allsky report for 09/15 from ~10pm

Cleardarksky forecast for 09/15 from ~10pm

Forecast from meteoblue for 09/15 from ~10pm

Guider results from 09/15 at ~11:49pm.

Indi Allsky chart for the morning of 09/16/23 showing a jSQM as low as ~2800 (remarkably good skies) at 4am.

Since Gamma Cygni is only visible from the deck until ~2am, set up a second target... California Nebula (NGC 1499/Sh2-220). 

Analysis window following collection on 09/15/2023 for both Gamma Cygni nebula as well as the California Nebula (NGC 1499/Sh2-220).  

In the morning (~08:45) collected 30 flat frames with the OTA pointed to zenith and 30 flat darks with the OTA covered and pointed at the ground.

Gamma Cygni Nebula from collection on 09/15/2023 from 49x180s lights (147 minutes)

NGC 1499 (California Nebula) from 09/15/2023 from 37x180s lights (111 minutes)

After cropping, light pollution and calibrating the background within Astro Pixel Processor (and cropping to the center of the field of view), the results without any calibration frames seemed fine.  A bit more processing was required in Astro Pixel Processor...and there are definitely hot pixels remaining in the final images...but otherwise calibration frames (in general) for the Canon T3I seem less helpful that one might hope.  Flat frames definitely would have aided in processing and likely would have resulted in a less severe crop.