Heart & Soul Nebula Mosaic Project

Goal:  Patch together collection over 14 total nights (10/2 through 11/20) into a giant mosaic using Astro Pixel Processor.  This all collected from the venerable Orion ST80 with a generic (ebay) dual narrow-band filter, the Canon T3I (astro modded) on the workhorse... Celestron CGEM DX (on franken-tripod).

Pre-processing & mosaic creation steps based on the tutorial found here.

Started with creation of individual panels composed of the integration of ~100 shots each.  All of these are 180s at ISO1600 with similar weather (temperature) making the selection of darks and bias frames uniform with one master dark and one master bias.  

However, camera orientation changes and re-focusing means two sets of flats and flat/darks across these nights (and realistically, perhaps more should have been captured... but with focus being fixed and camera orientation consistent across the two groups of sessions (one with camera in a horizontal orientation when the mount was parked and the second set of nights with it oriented vertically), it seems like relatively low risk to stick with just two sets of flats.  An additional potential complication, one set of flats (the first set) were captured against a white monitor... the second set against morning sky (which may motivate collecting a third set against the same white monitor background for greater consistency).

The individual nebula were captured and processed individually (here and here).  Within Indi/Ekos/Kstars, the mosaic tool provided a handy mechanism to define a set of four jobs for the Indi/Ekos scheduler that can be run and re-run.  Each job used a sequence file with 50 collections at 180s each at ISO1600.  The four panels spanned the space around both nebula in a 2x2 arrangement.

Results here with an initial set of four panels. 

Keeping track of all the frames and their distribution in the sky is impossible to do without actually building the mosaic... and the initial attempt clearly indicated a need for additional panels in order to create a rectangular region around the two nebula.  To plan additional locations for collection, found the Aladdin Sky Atlas software package incredibly useful in visualizing the location of the frames. As a Java application, it runs fine under Fedora 32/33.  

However, Aladdin lacks support for native DSLR files (like Canon CR2's from raw collection).  Adapted a bash script to utilize the solve-field command from the astrometry package to generate FITS files for all the CR2's within a subdirectory:

#!/bin/bash

### Use astrometry-engine to plate solve all Canon CR2 raw pictures in the directory and write out kml to current directory and fits to "fits_r
esults"  

for f in `ls --color=none *.CR2`;
do
echo $f
sem -j20 "\
nice -n 19 solve-field --dir /home/koehler/images/Astro/20201109_IC1848_Soul/fits_results --backend-config /etc/astrometry.cfg --downsample 4 -
-no-plots --kmz $f.kmz --timestamp --scale-low 2 --scale-high 5 --scale-units dw --ra 43 --dec 59 --radius 20 $f"
done
sem --wait 

Results from Aladdin suggested additional panels to not only square up the mosaic, but also fill in weak areas.  The final map of all panels for the mosaic is here.

The final squared up mosaic from the integration of all of these panels using Astro Pixel Processor is here: