M 42, M43

 Posted: Feb 6th, 2023
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NGC
IC
HD
Technical Info
Telescope/Lens: Synta bk 90/900
Camera: Nikon D5600
Mount: EQ 3-2 EQDrive Belt Upgrade
Software: DSS, FITStacker, Photoshop, Fitswork.
Exposure:
147 x 15" ISO/Gain: 3200
Orange zoneLight Pollution:
 Feb 4th, 2023
37 m
1419
Because I was shooting with an achromat, strong chromatic aberration appeared around the stars. Can you suggest how to effectively suppress it?
Resolution: 3916x3596 px
Scale: 70054 KB
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Comments

It turned out quite well!
I read somewhere about this method for reducing chromatic aberration in Photoshop:
- Convert the image from RGB color space to Lab (Image > Mode > Lab color);
- In the Layers window, go to the Channels tab and apply the Dust & Scratches filter (Filter > Noise > Dust & Scratches) to the a and b channels (*especially* the b channel), adjusting to taste;
- Convert the image from Lab back to RGB.
6 Feb, 2023 Reply
Astrodude Replied to Praeger
I tried it, and it works very well and quickly. The blue tint on the stars is gone. Thank you very much.
8 Feb, 2023 Reply
Praeger Replied to Astrodude
Please note! You should be more careful with these methods of combating chromatic aberration—they can "wash out" the natural color of blue stars and affect the color of non-stellar objects in the image (nebulae, galaxies, comets, etc.). The most correct approach would be to separate the processing of stars and everything else.
8 Feb, 2023 Reply
Search online. Removing chromatic aberration in astrophotography
Article by Star Hunter.
8 Feb, 2023 Reply
Also, you have a Nikon—I don’t remember the model name—but if you shoot in RAW, it doesn’t really matter what ISO you set; the result will be pretty much the same, though the dynamic range does drop. Try shooting at the same shutter speed with different ISO settings, but make sure you shoot in RAW, then play with the files in Photoshop. You’ll see there’s almost no difference. It’s just that at ISO 3200 you can see the image clearly on the screen, while at ISO 100 it looks like nothing is there—but the data is actually captured.
8 Feb, 2023 Reply
Astrodude Replied to Oleg Novoselov
Okay, thanks, I'll give it a try.
8 Feb, 2023 Reply

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