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  #1  
Old 13-10-2017, 04:02 PM
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sungrazer (Karen)
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Pleiades

Hi All

It has been a while since I have posted anything

I've processed a few shots and comparing my results with images on the web etc.

I got to wondering why I always seem to have these halos around bright stars, like in the horsehead and Alcyone in the Pleiades?

This is my shot of the Pleiades. I'm using an ED80 with a QSI683wsg - I take darks and flats and bias frames and use pixinsight to work with them - I still have a lot to learn about processing but just getting the round halos out would be a nice ambition.

Can anyone direct me to a good tutorial? or suggestion?

cheers
Karen
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  #2  
Old 13-10-2017, 07:42 PM
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billdan (Bill)
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Hi Karen,

Halos around bright stars are an astro-photographers curse I'm afraid and there isn't much that can be done to cure it.
What happens is the energy in a bright star is enough to bounce off the CCD chip back onto the camera glass window and then reflect back to the chip out of focus.
It happens with my QHY12 as well, so I avoid DSO's with bright stars in them.

Otherwise a very nice image of M45.

Cheers
Bill
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  #3  
Old 13-10-2017, 08:14 PM
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Got some good depth there. Too much green in the image. Pleiades is quite bluish. Try ACNR to get rid of the excess green and it'll make the colour balance a lot easier.

Halos. Try shorter subs.

Halos like that are from reflections. Are you using a reducer?
What brand filters are you using? Perhaps they don't have adequate anti reflection coatings. Astrodon Gen 1 filters developed halos when the larer 16803 sensor came out. They brought out Gen 2 filters with superior antireflection coatings and those sorts of halos became a thing of the past or at least not very common.

Greg.
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  #4  
Old 14-10-2017, 01:29 PM
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thanks

Quote:
Originally Posted by gregbradley View Post
Got some good depth there. Too much green in the image. Pleiades is quite bluish. Try ACNR to get rid of the excess green and it'll make the colour balance a lot easier.

Halos. Try shorter subs.

Halos like that are from reflections. Are you using a reducer?
What brand filters are you using? Perhaps they don't have adequate anti reflection coatings. Astrodon Gen 1 filters developed halos when the larer 16803 sensor came out. They brought out Gen 2 filters with superior antireflection coatings and those sorts of halos became a thing of the past or at least not very common.

Greg.
10-minute subs
astronomics filters
might have to switch - not very happy with them in general - I would have thought the focal length of the set would match and I wouldn't have to refocus between them - green is always the outlier and seems to need more focus correction than the others.

thanks for the advice. I will have another look at the ACNR in pixinsight and 5-minute subs and a lot more of them


cheers
Karen
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  #5  
Old 14-10-2017, 01:32 PM
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thanks
one should avoid bright stars altogether then :-)

Last edited by sungrazer; 14-10-2017 at 10:23 PM.
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  #6  
Old 14-10-2017, 02:01 PM
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Quote:
Originally Posted by sungrazer View Post

Can anyone direct me to a good tutorial? or suggestion?

cheers
Karen

Hi Karen.
You can do anything in Photoshop using blurred layer masks.
Mask each halo one at a time & work on it with the colour & brightness.
Ken Crawford explains masks here:
http://www.imagingdeepsky.com/Tutori...LB_Stream.html
but not for your exact problem.

cheers
Allan
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  #7  
Old 14-10-2017, 02:47 PM
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Looks pretty good. You got a lot of neb in the shot. Halos are always hard to get out unfortunately. Masking in PS is the only way I know about doing it but even that is not perfect especially on the edges of the mask.

PS: added blink. You make a round selection, feather it then copy/paste the halo on top, set is as linear burn or screen or another filter then play with the transparency. That's the idea anyway. You then need to spend some time refining the colours, levels and edges.
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  #8  
Old 14-10-2017, 10:53 PM
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thanks

Quote:
Originally Posted by multiweb View Post
Looks pretty good. You got a lot of neb in the shot. Halos are always hard to get out unfortunately. Masking in PS is the only way I know about doing it but even that is not perfect especially on the edges of the mask.

PS: added blink. You make a round selection, feather it then copy/paste the halo on top, set is as linear burn or screen or another filter then play with the transparency. That's the idea anyway. You then need to spend some time refining the colours, levels and edges.
Love the blink. :-)

I'm happy with it in general - I would prefer to have a flatter image - less noise in the dark areas and a bluer image too. But yes very happy with the nebulosity. I was super pleased with that, since Pleiades is a hard shot for me to get. Patience over months .... My obs walls are a bit high so shooting times are short.

thanks for the tip - Bloody photoshop... It's why I bought Pixinsight... :-) back to square one then eh!
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  #9  
Old 14-10-2017, 11:04 PM
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thanks

Quote:
Originally Posted by alpal View Post
Hi Karen.
You can do anything in Photoshop using blurred layer masks.
Mask each halo one at a time & work on it with the colour & brightness.
Ken Crawford explains masks here:
http://www.imagingdeepsky.com/Tutori...LB_Stream.html
but not for your exact problem.

cheers
Allan
Hi Allan

Thanks very much. I have much to learn from kens tutorials !
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  #10  
Old 15-10-2017, 06:22 PM
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Looking good, Karen. Impressed with Marcís treatment of the halos as well. I tend to avoid Pleiades, too darned hard with the STL but you have given it a good go.
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  #11  
Old 15-10-2017, 07:03 PM
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Quote:
Originally Posted by DJT View Post
Looking good, Karen. Impressed with Marcís treatment of the halos as well. I tend to avoid Pleiades, too darned hard with the STL but you have given it a good go.
thanks :-) its one of my fav's

I really wanted the red/grey to come out not just the blue - still there is more work to do on it
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  #12  
Old 16-10-2017, 04:12 PM
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if you have I would also try to get rid of the excess green and the colours will balance better. Try SCNR on it.

Greg.
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  #13  
Old 17-10-2017, 11:32 PM
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Quote:
Originally Posted by gregbradley View Post
if you have I would also try to get rid of the excess green and the colours will balance better. Try SCNR on it.

Greg.
will do

thanks
Karen
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  #14  
Old 18-10-2017, 01:52 PM
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Quite a nice M45 Karen with plenty of nebulosity showing and I actually like the colour balance. Marc has shown a good approach to reduce the impact of the Halos too.

Mike
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  #15  
Old 21-10-2017, 10:43 PM
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Quote:
Originally Posted by strongmanmike View Post
Quite a nice M45 Karen with plenty of nebulosity showing and I actually like the colour balance. Marc has shown a good approach to reduce the impact of the Halos too.

Mike
Thanks Mike
that means a lot
cheers
Karen
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