Halos in Stars
Stacking program, astrometric (plate) solver, fits file viewer
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han59
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Hi everyone, I'm starting to use ASTAP to stack my images. It was working well, but I ran into a problem with Rosetta: the stars have a really ugly halo, especially those in the nebula. Is there any way to control that?
Other stacking programs don't do this at all.
Hi Daniel,
Yes that doesn't look nice. An improvement was added a few months month ago. Have used the latest ASTAP version?
If so, can you share the seperate L, R,G, B stack files (4 files) so I can have a look myself?
cs, Han
Hi, I'm using ASTAP 2026.04.21 64-bit. My camera is OSC; I don't have R, G, and B outputs, and I only have one output file. Do you need it?
The most likely problem is the star colour smooth setting. If you uncheck it (see attached) then it will be gone but the colour of the star is not fully homogeneous due to the Bayer pattern of the OSC image.
The program tries to smooth the star colours but the star colour is mixed with the red cloud background. The red background is included because it is above 3 sigma.
What I would do is stack the image with "Colour smooth" unchecked and use the indetical function in tab pixel math 1, menu "Global colour smooth" (second column of functions). And try something like 5 & 6. The second value is the level above background which would be included in the smoothing.
You could also try in tab pixel math1 the option "star colour smooth". After each try you can go back or use ctrl+Z and retry.
If you share some of your OSC raw images, I can have look here as well to see which setting works best for you
Sometimes the switching between debayer method Astro-C or Astr simple help.
cs, Han
Thanks Han! I'm going away for two months, so when I get back I'll try your suggestions. I'll send you the FIT file where I found the problem; take a look at it when you have time.
Thanks again. Cheers
P.D. (I can't add my file...)
No problem, I just got some new idea to improve the algorithm, so try a new ASTAP version when your back.
I'm still interested in the stacked file without the option "Colout smooth checked". Normally you should be able to attach a large FITS file. If not drop it at site: ufile.io
and send me the link. Then I can experiment with it.
Han
I had a look to some other images with a bright red nebula. Try the the following:
Uncheck Global colour smooth
Check mark Fix colour saturated stars.
See attached
You could try this also in Pixel math 1 with an image these options where unchecked.
cs, Han
I'm sending the stack with default settings. No Flats, Darks, or Bias.
We'll talk when I get back.
https://ufile.io/fh0a1jsu
Okay.
Next ASTAP version will have a fix for the global "star smooth" function. This should fix your problem