Star Removal - At what stage should they go?

[AMcD]

I am currently finding my way with processing LRGB images.  Is there a recommended point in the processing workflow at which to undertake star removal and replacement?  My instinct says after channel combination but before further processing...

[Budgie1]

Although I use OSC, I normally remove the stars either prior to the stretch (so I can stretch the stars separately) or right after. This allows for more controlled use of Curves etc on both parts of the image. 

I normally re-integrate the stars right at the end of processing, so after all adjustments & noise reduction have been completed on the background. 

[ollypenrice]

Instinct told me to do it early but experience hasn't borne this out.  I've had excellent results by going over old 'finished' images and de-starring them. I find I can them stretch them still further, with advantage - and especially if I give them a dose of NoiseXterminator as well.

I then recombine them following Ciaran's advice on here. (Photoshop, paste starless over starry, invert both, top layer active, change blend mode to divide, stamp down (CtrL/Shift/E), invert top layer, flatten and save as stars. Paste this on top of starless, blend mode screen, then simply de-stretch to taste using the mid point slider in Levels.

If working on new data I compromise, de-starring after a partial stretch.

I find StarX works 9 times out of 10 but sometimes throws up a fatally checkerboard background too visible to fix cosmetically.

Olly

[gorann]

1 hour ago, ollypenrice said:

Instinct told me to do it early but experience hasn't borne this out.  I've had excellent results by going over old 'finished' images and de-starring them. I find I can them stretch them still further, with advantage - and especially if I give them a dose of NoiseXterminator as well.

I then recombine them following Ciaran's advice on here. (Photoshop, paste starless over starry, invert both, top layer active, change blend mode to divide, stamp down (CtrL/Shift/E), invert top layer, flatten and save as stars. Paste this on top of starless, blend mode screen, then simply de-stretch to taste using the mid point slider in Levels.

If working on new data I compromise, de-starring after a partial stretch.

I find StarX works 9 times out of 10 but sometimes throws up a fatally checkerboard background too visible to fix cosmetically.

Olly

That checkerboard happened to me once, but then I think it was a slightly earlier version of StarXT than the one I use now. However, sometimes it leaves a few star halos. In that case I try Starnet2 in PI and it may work better. It is free so well worth getting.

[drjolo]

I use Starnet++ to remove stars on semi stretched images - so then after star separation there is still a room to both process the stars separately and stretch the nebulosity more.  Removing stars with Starnet is quite simple, so it is easy to play a little and check what stretch amount will give the best result in the starless image. 

 

Edited November 18, 2022 by drjolo

[AMcD]

4 hours ago, ollypenrice said:

and especially if I give them a dose of NoiseXterminator as well.

Many thanks Olly.  The idea of “dosing” my data with various applications made me laugh.

I almost have a complete set of LRGB data on the Elephant Trunk nebula so am keen to try a complete workflow on mono data.  It is clear here at the moment so I might get my blue channel- although I am probably speaking too soon 🙄

[AMcD]

1 hour ago, drjolo said:

I use Starnet++ to remove stars on semi stretched images - so then after star separation there is still a room to both process the stars separately and stretch the nebulosity more.  Removing stars with Starnet is quite simple, so it is easy to play a little and check what stretch amount will give the best result in the starless image. 

 

Beautiful images.  Quite stunning.

[ollypenrice]

3 hours ago, drjolo said:

I use Starnet++ to remove stars on semi stretched images - so then after star separation there is still a room to both process the stars separately and stretch the nebulosity more.  Removing stars with Starnet is quite simple, so it is easy to play a little and check what stretch amount will give the best result in the starless image. 

 

Stunning result. Both star removal tools work best on narrowband, which is not surprising, really, since NB stars are smaller with tighter edges and can, therefore, be spotted more easily by the software.

Olly