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Questions & Answers/Tips & Tricks => Digital and Film Astro Imaging => Topic started by: PaulB on 13:12:53, 29 December, 2017

Title: How do I remove a DSO in CS5
Post by: PaulB on 13:12:53, 29 December, 2017
Hey guys
I need some advice. How do you remove a DSO. M76 in this case. So I can work on the background. And remove gradient's
Title: Re: How do I remove a DSO in CS5
Post by: Nimbus on 14:25:05, 29 December, 2017
Paul from memory open the image. Duplicate layer.  Select highlights in top layer. Expand by 2 pixels Feather by 1 and cut. Sorry I am out and away from my PC so don’t have the drop diwn menus in front of me.

This is the simplest approach. This leaves the nebula. Paste the stars into another layer and save for later. Work in the nebula and background. Then using layers set the more mode to screen and adjust to make star look more natural.

If you can’t follow the above I will look to more detailed nstruction after I get home.

HTH Jim

Title: Re: How do I remove a DSO in CS5
Post by: PaulB on 15:07:46, 29 December, 2017
Thank you, Jim

If you can help me I would appreciate it.
Title: Re: How do I remove a DSO in CS5
Post by: Nimbus on 17:25:47, 29 December, 2017
OK Paul now back home:
Open image, Duplicate Image in Layers,
Select Upper Layer
Select, Colour Range, Change drop down to Highlights, Click OK,
Select, Modify, Expand, 2 Pixels
Select Modify, Feather, 1 Pixel
Edit, Cut
(If you deselect the eye on the lower layer you can see the checker board design below showing there are holes in the upper Layer.) Select Eye on lower Layer and the stars reappear and at this stage the image looks as it started.
Play with the Upper Layer to achieve the effect you want (DO NOT WORK on the lower Layer)
When happy ensure the eye is ticked on the lower layer, there will be artefacts around the "stars" in the upper layer. 
Working on the lower Layer only brighten the image using Levels this will increase the brightness of the stars and expand them to fill the holes in the upper Layer - when happy i.e. no Black rings around the stars - flatten the image and continue.

This is perhaps the simplest way of achieving what you want to do albeit a bit crude but it will get you most of the way.  There are other techniques which are much more complex.  Normally, I use the Stratton Star Removal software (EXCELLENT!) to remove ALL the stars and then add the stars back in from the original image but that is another story..  See how you get on with the above and come back to me if you need some more pointers.

HTH Jim
Title: Re: How do I remove a DSO in CS5
Post by: Carole on 21:37:44, 01 January, 2018
In photoshop, I normally draw a feathered lasso around any areas such as nebulae and bright stars I don't want affected by GE, and then select inverse and do the Gradient exterminator.

If you want to select more than one area, you need to press another key at the same time, I think it's either shift or control, (can't remember which but it's one or the other).

Carole
Title: Re: How do I remove a DSO in CS5
Post by: PaulB on 21:45:49, 01 January, 2018
I had not thought of doing that.
Thank you, Carole.

Happy 2018
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