M13 - ZS66, ASI485MC

[Ags]

This is 33 minutes of 4-second subs, shot with my AZGTI in alt-az mode. I did not use a reducer/flattener (to get a bit more scale), so the stars are not perfectly round throughout. I tried shooting at 300 gain as an experiment. Another experiment was keeping the data linear for almost all the stretching. Processed in Gimp. I tried enhancing the color with Colors > Auto > Color Enhance (a new tool to me) although it was rather too strong so I toned it down with layers. As a final experiment I used Siril to remove a gradient.

Edited May 14, 2023 by Ags

[Ags]

I did a reprocess doing color balance and background extraction in Siril before doing further processing in Gimp. I've got more of the cluster, but less of the star color in the bright field stars. It's stretched so much the imperfections of my field rotation are starting to show through - to get rid of that I either need to find my polar scope and go EQ or do the stack in Siril and do background extraction on each subframe.

Edited May 15, 2023 by Ags

[Ags]

I was just reading about Siril star synthesis which can desaturate stars using science and make star shapes more perfect using art. This could take my M13 to the “next level” 🤣

I’m quite liking Siril - unlike AstroPixelProcessor I understand what it is doing and feel I can use it logically… 

Edited May 15, 2023 by Ags

[Ags]

OK, it's me again! This time I took the DSS stack into Siril, where I did color balancing, gradient extraction, star desaturation, and noise reduction. Then I put the image into Gimp for stretching, sharpening and color enhancing. I think this is the final version? Happy to have color in the stars in M13 and the blue star at 7 o'clock is looking bluish not whitish. I may have pushed the sharpening too far though.

I got the color by using adding the unstretched image as a layer, running Color Enhance, and setting the mode to HSL Color.

Siril noise reduction has features specifically for the light starved images I take, and it helped reduce the noise shadow from the field rotation quite well.

Edited May 16, 2023 by Ags