Jump to content

Narrowband

PI - Stretch bright target while retaining faint background?


Recommended Posts

I took 2hr27min of M57 last night with our SW200dps & Canon600d. I'm trying to process it, but M57 is very bright compared to the rest of the objects in the sky. If I stretch the image to bring out the nebula I lose the faint detail such as the barred spiral galaxy IC1296, but if I apply a 'normal' ScreenTransferFunction stretch, the nebula is completely washed out.

What's the best way to proceed? Should I process both & recombine with PixelMath, or Mask M57 & apply different stretches to the nebula & background?

I'm early on in the workflow, having just done background removal, BN & PCC (so no noise reduction yet). Screen Grab shows the 'normal' STF & a MaskedStretch applied to a preview.
 

Any help much appreciated!
Cheers
Ivor

M57_Query.JPG

Link to comment
Share on other sites

I use arcsinh stretch for rgb images, and follow up with curves stretch. Here, I pin the high end of the scale so the curve is straight for values I don’t want blown out, and only stretch the lower end. For L, I use histogram stretch in several iterations, with the midpoint slider at 0.25, until I get a pleasing image with a weak background. Then I switch to curves as per above. Sometimes I use multiscale hdr transform with a 50% mask to reduce overly bright areas a little. This workflow allows control over bright and dark areas.

HTH,

  • Thanks 1
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
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • 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.