OIII star bloat

Questions and answers about processing in StarTools and how to accomplish certain tasks.
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astrosatch
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Joined: Fri Sep 04, 2020 9:51 am

OIII star bloat

Post by astrosatch »

Hi!
Is there a way to reduce star bloat in OIII channel? My OIII channel has bigger stars than that of Ha and SII and when combined there is this blue ring around stars which is quite annoying. When shrinking stars is even more pronounced. There was mentioned to shrink stars in OIII channel and then combine with Ha and Sii afterwards. Is this possible with Startools?

Thank for help.

Andrej
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admin
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Re: OIII star bloat

Post by admin »

Hi Andrej,

There are many techniques you can employ to reduce star bloat and halos.
Which ones to use depends a little on the dataset (exposures, filters used) and your goals.

If you could post a crop of your image showing the problem that would help.

For example, if you are doing a SHO composite and you find the O-III channel is not that good, you can simply decide to just use it for the coloring (chrominance) only by setting its exposure time to 0 (for the purpose of your synthetic luminance) when using the Compose module. This will completely avoid using the O-III for any detail, but will still show all O-III emissions for the coloring of the Ha+S-II-only detail.
Ivo Jager
StarTools creator and astronomy enthusiast
astrosatch
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Joined: Fri Sep 04, 2020 9:51 am

Re: OIII star bloat

Post by astrosatch »

Hi Ivo. Thanks for your reply. I've tried that and with not much success. However I found one way to deal with blue rings around stars. In Shrink module if I set color taming to several pixels, blue rings dissipates into background which is exactly what I want. But then star color suffers as well. If I set this too high, smaller stars looses color altogether. Do you have any recomendation to deal with this issue? How do I mask only smaller stars without all single pixel noise that get included?
Thank you.

Andrej
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Re: OIII star bloat

Post by admin »

astrosatch wrote: Fri Mar 12, 2021 11:23 am Hi Ivo. Thanks for your reply. I've tried that and with not much success.
Hmmm... that is very strange - in that case the problem is not your O-III, but rather something in your optical train that is affecting all channels.
It's a little difficult to diagnose the problem or help you without seeing the issue.
Ivo Jager
StarTools creator and astronomy enthusiast
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