Telescope Reviews: Achieving color in galaxy shots

I did a quick processing on the sample data you posted. Obviously, the noise is very high since there's less than 3 minutes of total exposure and the data was captured from a red zone. As such, I was limited to how much I could stretch it and how much can be shown in the image. However, I think you can see that the galaxy's spiral arms have a blue color to them, while the core is heading towards a yellow/red color. These are typical colors I expect from M81.

When I compare it to your original image, it appears that your image lacks much of the blue, and the core is much redder than my processing of your 4x40 subs. Also, when I processed your original 32 bit Tiff, I had to push blue into the galaxy in order to have similar colors.

My gut suspicion is that there's something you're doing in your pre-processing that is altering the colors or removing some of the color. I'd be hard pressed to tell you what it is, but I didn't have to do anything fancy with my processing of the 4x40 subs to bring out blue in the galaxy.

If it'll help, here's the basic workflow I did with your data:

1) Used Images Plus 5.0 for automatic processing (generate master dark, generate master flat, convert CR2s to FITs, calibrate lights, normalize lights, align, and combine). This is a lot of steps, but IP does it all automatically after you point it to the data files.

2) Initial DDP stretch in Images Plus 5.0 - settings of Break Point 10,000, Background Weight .92, Scale function nth Root X^n, Root .820

The rest of the processing was in Photoshop CS5:

3) Gradient Xterminator

4) Levels - set initial grey point, set initial black point.

5) HLVG - Medium setting. Removes some of the green pixel noise.

6) Mild stretching curve

7) Carboni Deep Space Noise Reduction

8) Another mild stretching curve

9) Saturate using Block Method - 3 times

10) Levels - set final white and black points

Other than saturating and HLVG, there's nothing in this workflow that would have affected the color balance in the image (the HLVG would have taken out some green, so the image is very slightly more magenta). Certainly there's nothing here that would have pushed blue into the spiral arms.

I'm not sure if this is helpful, but hopefully it may give you some ideas about where to look for your lost color. Please let me know if you have any questions or thoughts.