Spooky avatar
This is my first picture of M42 with a startracker.
You can find the acquisition/processing details in the description of the picture.

Orion's Belt


Thanks
dkamen avatar
Hi,

With only 30 second subs you are bound to have more colorful stars (unless you used an extremely high ISO) because you haven't exposed enough to burn them into white.  Most of the large stars should be blue and most of the small ones should be orange. There should also be a lot more green and blue in the big nebula, even at such little total exposure.

Overall, the image has much less color that I'm sure you have available in your raw data (unless, I repeat, the ISO was extremely high). It's practically black+white with a few faint shades of red.

I think this is because of your workflow. I see you do two stretching steps (asinh and and histogram), then color calibration and background extraction and then photometric color calibration and another stretching

Thing is, both background extraction and color calibration (photometric and traditional) are designed to run on linear data, but stretching removes linearity.  Therefore background extraction removes more than it should and color calibration cannot calculate the correction factors properly.

The first step in your post processing workflow should always be background extraction -since background is completely worthless signal- followed by color calibration OR photometric color calibration (not both). Then everything else (especially asinh and histogram stuff which break linearity). I think if you try it you will see major improvement, because detail-wise your result is actually very very nice for a first picture.

Cheers,
Dimitris
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Mark Germani avatar
Thing is, both background extraction and color calibration (photometric and traditional) are designed to run on linear data, but stretching removes linearity.  Therefore background extraction removes more than it should and color calibration cannot calculate the correction factors properly.


This is really useful info - thanks Dimitris!

Nice work, Spooky! From a purely aesthetic standpoint, I'm a little thrown by the rotation of the image; I'm more accustomed to seeing M42 under the belt rather than to the right of it, and I might crop the shot slightly to centre M42 and the belt in the frame. But I'm new here, so you can take that with a grain of salt

Thanks for sharing!
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