IC 63 and IC 59 - dealing with lousy images

As I wanted to focus on IC 63, I decided to use my dual-band filter.

I knew, this mission would pose some challenges, but I did not know it would be so hard:

• The sky was not very clear and the objects were descending, thus the air mass was becoming worse over imaging time.
• The moon was very bright.
• The objects are extremely faint and hardly visible even on a 240s exposure, my signal hardly exceeded the sky glow.
• Balancing my scope was tricky, my tracking guidance was something between perfect and nonexistent.
• I somehow ruined my camera settings (gain and offset), as I tried to capture the Jupiter / Venus constellation and ASICap adjusted the camera and the values were not restored properly when doing the exposures for the nebula. It was almost impossible to subtract the master dark from my library.

Let's start with a look at a 240 seconds sub first. IC 63 marked with blue, IC 59 marked with orange.

I had to throw away about 20% of my subs. From my 5 nights session, only 167 subs were suitable, resulting in an overall imaging time of 11 hours. For other objects, this would be a fantastic overall exposure time.

Caused by the issues I had with gain and offset and the need to take additional flats as there was some movement in the optics during the 5 days, I head to experiment a lot with SiriL and the scripting. My final stacking results for H-alpha and OIII showed lots of issues: Sky glow, reflection from Gamma Cassiopeiae, stacking artifacts and some bad background behavior (H-alpha left, OIII right):

But as I had already spent hours in capturing and stacking, I decided to give post-processing a try.

I started with my standard workflow I am using for dual-band filter images but failed completely as I could not find a way to properly subtract the background without terrible artifacts.

So I decided to combine the images first to a color image, use Starnet++ to remove the stars and subtract the background from the nebula, using PixInsight's DBE, followed by an ABE with default settings.

Another issue was the proper application of BlurXTerimator. I found that Starnet++ leaves artifacts, if the stars were sharpened by BlurXterminator, so I had to decouple the workflow for nebula and stars:

• Use BlurXTerminator for sharperning the nebula only (no star sharpening) and remove the stars with Starnet++ for a sterless image of the nebula without artifacts.
• Use BlurXterminator for sharperning the stars only and Starnet++ to create a star mask, so the nebula can be combined with sharp stars afterward.

With some ArcsinhStretch and noise removal using ACDNR, the nebula image still was terrible:

After a recombination with the sharpened stars, at least the blotchy noise was less visible, but the image still had lots of color gradient and the reflection of Gamma Cassiopeiae:

So I decided, to further process the image in Photoshop, using

• AstroFlat Pro for further background reduction,
• TopazDeNoise AI for further noise reduction,
• Astronomy Tools for enhancement of the deep sky object structures,
• and some masked painting to get rid of Gamma Cassiopeiae.