Forgive me if this has been addressed before. What is the cause and the fix for the small halos around stars (especially around the fainter ones)?
Michael
Star Halos
Re: Star Halos
Hi Michael,mhamburg wrote:Forgive me if this has been addressed before. What is the cause and the fix for the small halos around stars (especially around the fainter ones)?
Michael
Any chance you could post a small (processed) crop of the problem?
Halos are caused by a number of things. If all your optics are perfect (e.g. we can rule out focus and chromatic aberrations), then the usual culprit is atmospheric turbulence (aka seeing), as well as your telescope's diffraction pattern.
Ivo Jager
StarTools creator and astronomy enthusiast
StarTools creator and astronomy enthusiast
Re: Star Halos
Look especially at the fainter stars. Could this be an artifact from some type of masking during processing that I somehow didn't do correctly?
Michael
ps. When I look at a crop of the star field, now I only see that there is a focus problem. I no longer see the halos!!!
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Re: Star Halos
Hi Michael,
The stars don't appear offensive to me at all
Could you describe the problem/symptom a bit more and also describe what you would expect to see instead?
Due to your scope's diffraction pattern and (possibly) atmospheric conditions, stars will never appear perfectly pin-point.
StarTools' clipping protection also ensures your stars are never blown out/clipped (sometimes you see these perfect blown out circles in other images from other software). This will indeed preserve (but not create!) halos, but they are real image data (and contain important information about star coloring). This behaviour can be quite important too for retaining detail close to overpowering stars (e.g. Alnitak) or stars shrouded in nebulosity (ex. Iris nebula).
However, if the halos bother you, try the Magic module's "Tighten" algorithm on the offending stars (and their halos) in a star mask. this algorithm was specifically designed to 'Tighten' the halos around the stars towards their core.
The stars don't appear offensive to me at all
Could you describe the problem/symptom a bit more and also describe what you would expect to see instead?
Due to your scope's diffraction pattern and (possibly) atmospheric conditions, stars will never appear perfectly pin-point.
StarTools' clipping protection also ensures your stars are never blown out/clipped (sometimes you see these perfect blown out circles in other images from other software). This will indeed preserve (but not create!) halos, but they are real image data (and contain important information about star coloring). This behaviour can be quite important too for retaining detail close to overpowering stars (e.g. Alnitak) or stars shrouded in nebulosity (ex. Iris nebula).
However, if the halos bother you, try the Magic module's "Tighten" algorithm on the offending stars (and their halos) in a star mask. this algorithm was specifically designed to 'Tighten' the halos around the stars towards their core.
Ivo Jager
StarTools creator and astronomy enthusiast
StarTools creator and astronomy enthusiast
Re: Star Halos
Thanks for the reply, Ivo. The halos seemed to have disappeared when I saved the original .tif to a .jpg format. (Or maybe I have been looking at these images for too long? )