PixInsight Forum (historical)

PixInsight => General => Topic started by: RenaudVL on 2019 December 30 23:32:23

Title: Huge reflection halos!
Post by: RenaudVL on 2019 December 30 23:32:23

Hello all,

I am using a Celestron C9.25 Edge HD with dedicated 0.7x reducer and Moonlight focuser with proper spacer for my QHY168C.

Mounted the Optolon L-Pro 2" filter on the nose piece.

I get huge reflection rings on my image around big stars!

Would there be a way to remove those with pixinsight ?

Any advice would be welcome!

Thank you

Title: Re: Udge reflection halos!
Post by: John_Gill on 2019 December 30 23:58:33

Hi,

I have had similar problems with my 8"EdgeHD.  Anyway, try this for a synthetic flat to remove the halo.

Open unstretched Light image and apply STF
Duplicate image and name star_support
Duplicate image and name flat

MMT - 5 layers
X on Residual
Apply to star_support image

PixelMath $T - star_support
Apply to flat

MMT  - 6 Layers
X all layers except Residual
Apply to flat

CloneStamp bright areas
PixelMath $T * mean(flat) / flat
Apply to Light

I am sure there are many other better way to fix this, but this seems to work quite well.

Space is not black
John

Title: Re: Udge reflection halos!
Post by: dave_galera on 2019 December 31 04:22:33

Give it a try without the Filter and/or reducer to see if you can identify what is causing the problem.

Also have a look at these articles:
https://www.cloudynights.com/topic/647402-asi1600mm-pro-halos-with-bright-stars/
and
https://www.cloudynights.com/topic/636825-help-my-jellyfish/?hl=%2Bhelp+%2Bmy+%2Bjellyfish#entry8892691

Title: Re: Huge reflection halos!
Post by: RenaudVL on 2020 January 05 11:38:26

Thank you John and Dave for your reply!
I'll look into it! 

Title: Re: Huge reflection halos!
Post by: pfile on 2020 January 05 16:12:34

there is also a script called StarHaloReducer which might help, but it wants to deal with circular reflections and yours looks a little oval.

it's a little obtuse but first you draw a preview around the halo you want to fix, then run the script. you then have to adjust the halo radius, star protection radius and amount to brighten or darken. if you set the sliders to exaggerate the correction you can more easily adjust the other sliders as the correction becomes very obvious. when you get it positioned right, then try to dial in the darkening amount.

rob

Title: Re: Huge reflection halos!
Post by: jkmorse on 2020 January 06 18:02:25

I just posted a way to remove dust donuts and there is no reason the technique I describe here: https://pixinsight.com/forum/index.php?topic=14538.0 wouldn't work for your issue as well. 

Worth a shot  ^-^

Best,

Jim