Jump to content

Walking on the Moon

Star Removal - At what stage should they go?


Recommended Posts

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...

Link to comment
Share on other sites

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. 

  • Thanks 1
Link to comment
Share on other sites

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

Link to comment
Share on other sites

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.

  • Like 1
  • Thanks 1
Link to comment
Share on other sites

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. 

spacer.png spacer.png

Edited by drjolo
  • Like 2
  • Thanks 1
Link to comment
Share on other sites

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 🙄

  • Like 1
Link to comment
Share on other sites

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. 

spacer.png spacer.png

Beautiful images.  Quite stunning.

Link to comment
Share on other sites

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. 

spacer.png spacer.png

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

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.