PixInsight Forum (historical)
PixInsight => Tutorials and Processing Examples => Topic started by: Alfredo Beltran on 2013 January 08 17:45:11
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Hi
I'm using currently a trial version of PixInsight and like it very much so far. A year ago I did this image of M45, which came with weird halos from reflections on the optical train:
http://www.astrobin.com/26317/
Can those halos be removed with a mask? I saw the blooming reduction with a mask in this tutorial (http://www.pixinsight.com/examples/NGC6914-CAHA/en.html), but could someone explain a step by step process?
Thanks for your help!
Alfredo
Bogotá, Colombia
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Hi Alfredo,
I'm not even sure it's possible to do what you're asking but it's certainly not a trivial operation. I'm certainly clueless on how to do that, sorry. The trouble is that the artifacts have very smooth transitions from faint to bright which makes them difficult to detect. They look just like DSO's.
Hopefully someone else will have a suggestion but when I run into situations like this like with my hyperstar I try to address it at the source, not in post processing.
Welcome to this forum and PI!
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Hi Sander
I was hoping that this could be removed like the blooming was removed. I just don't know PI enough yet. It's an amazing program.
I hope someone could really help me on this. I have these reflections on every bright star as can be seen in my gallery pictures:
http://www.astrobin.com/users/alfredobeltran/
I don't know if this could be a collimation issue or internal reflections on the C6 SCT. Have you seen this before?
Alfredo
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Hi Alfredo,
halos are very common and hard to avoid. Technically all stars in your images have halos but it's mostly visible with bright stars because the halo signal climbs high enough to be visible. SCTs are notorious for causing them but all optical systems are susceptible.
The artifacts in your Pleiades image aren't halos but a different type of artifact. Ultimately all caused by uncontrolled reflections. I had them with my C11 with hyperstar, called them Abyss Aliens. In the end I decided to skip targets with bright stars.
Anyway, start a little lower with PI and give basic processing a try before trying voodoo magic.
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A very good suggestion Sander! 8)
Nevertheless it's a little sad these reflections appear. There are so many targets with bright stars nearby...
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I understand your pain Alfredo, they have frustrated me too.
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these halos are caused by the main mirror baffle not being black enough on the inside. the solution is apparently to use some flocking paper to line the inside of the baffle.
i was trying to help this guy debug something on astrobin questions. i processed his image and came up with this:
http://www.astrobin.com/27095/
looks familiar, right?
http://questions.astrobin.com/question/601/how-can-i-improve-this-image-unprocessed-stack-of-raw-images-flame-nebula/
check the last answer jmel posted with his link to a thread on cloudynights with pictures of the solution. this problem seems to plague C6s and maybe C5s as well.
rob
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Hi Rob
This is exactly the same kind o reflections I'm having. I really appreciate you sent the link.
It seems indeed that is very common on certain kind of SCT telescopes and the solution appears to be easy to implement.
I will check my telescope to see if it is glossy on the baffle and if it is, I will implement the suggested solution.
Thank you very much indeed.
Best regards
Alfredo
Bogotá, Colombia
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no problem, i hope you can resolve it. astrophotography is hard enough without equipment problems!