Help With Getting Better Color In M31

[dhellis59]

Hi,

I have been working on M31 for some time now. I have compiled up to 8 hours of data with calibration files from 3 min subs to 15 min subs each stacked separately and combined after. I realize that this causes some challenger, and I will also process separately.

However, I am more concerned right now with learning how to get the most out of the data. Below is my latest rendition. The challenge I am focusing on now is how to bring out the color in the mid to outer portions of the DSO vs the center. It seems that all I can do is choose a white point and adjust the color for the whole image. How does one adjust color on different portions of the image? Also what else, capturing or processing wise, can be done to improve it?

M31 113 L 3 Darks 49 Flats 48 Dark Flats 48 Bias 092816.jpg (221.71 KiB) Viewed 4708 times

The fts data file can be found here: https://1drv.ms/u/s!AvMvsxCOFVCfjSfdV7pHKpMuGSs2

Please share your results and work flow so I can repeat it.

Thanks in advance for anybody that participates and contributes.

Darryl

[dhellis59]

Oh, I forgot to add, my imaging equipment includes a C80Ed Refractor on a CGEM DX mount. My camera is a Canon XSI 450D, and I use an Astro Tech Field Flattner. No filters were used in this image, but I do image from a red zone.

Feel free to ask me any questions you may have.

Thanks,

Darryl

[admin]

Hi,

Sorry for the late reply.

I had a look at the data, and you should be able to achieve good colors with a rather standard workflow, for example a workflow like this.
You'll be surprised at how easy the color calibration is..

Mirroring that workflow, I processed your image as follows.
I intentionally kept it really short to get to the color stage as quick as possible;

--- Crop
Upon loading, first I cropped away the stacking artifacts.
Parameter [X1] set to [716 pixels]
Parameter [Y1] set to [482 pixels]
Parameter [X2] set to [3357 pixels (-933)]
Parameter [Y2] set to [2379 pixels (-477)]
--- Bin
Next I binned the image to 50% to improve signal-to-noise. This data has deconvolution potential.
Parameter [Scale] set to [(scale/noise reduction 50.00%)/(400.00%)/(+2.00 bits)]
--- Wipe
Light pollution removal and color bias calibration.
Default parameters, however with parameter [Dark Anomaly Filter] set to [7 pixels] in order to make WIpe ignore any local dips caused by noise or dead pixels in this data.
I also masked out a dust donut and the core of M31, so that Wipe won't sample these (see also here).
--- Auto Develop
Final stretch.
Clicked & dragged a Region of Interest; a slice of M31, but not much background.
Parameter [Ignore Fine Detail <] set to [2.5 pixels] to make AutoDev optimise less for fine noise.
--- Color
Default parameters. Really! (see also here on how you can determine the color balance is indeed correct, as it is here)
Apply the color module at the end of your processing, just before switching Tracking off.

After these simple steps you end up with this;

M31 113 L 3 Darks 49 Flats 48 Dark Flats 48 Bias 092816.jpg (465.07 KiB) Viewed 4676 times

A text book M31 as far as coloring goes (yellowish core due to older stars, bluer outer rim with more star formation going on, nice evenly distributed foreground star field in terms of temperatures). Of course, you'll want to switch Tracking off, do noise reduction and maybe apply some decon/contast/HDR/sharpening/etc. after AutoDev, but that's up to you of course.

As for tips, I would definitely check your flats (with that dust donut coming through). Do you dither between frames?

Hope this helps!

[dhellis59]

Ivo!

Thanks, my man. You just don't know how much I appreciate you. I am sorry for my late response.

Huge difference in your result. Yes, I have to do a better job with my calibration files. Honestly, this is a hodgepodge of different imaging sessions, and I know I got my calibration files mixed up. I went through a period of fighting dust donuts and didn't know their origin or how to eliminate them. Now, I clean my camera regularly, and do collect calibration files more often, but still probably nowhere enough. I need to scrap it all and just start from scratch again, but I figured this would work for practice.

Thanks for the work flow tips and analysis. I have been getting more and more familiar with Star Tools, but the more I learn, the more I see there is to learn and tools and techniques to try. It is an awesome program.

Now with your guidance I am encouraged to dig further. Tell me about dithering though. I see that it is available in PHD2 and in Astrophotography Tool, which are the imaging programs I use, but am not sure how to initiate it or what it does exactly. Still learning...

Thanks again,

Darryl