Screen Stars Script

Adam

Have you compared the "Screen Stars Script" to the more traditional methods, like you demonstrated in your NB section?  I just saw the video on this script but haven't downloaded it and I normally use StarX to remove RGB stars from an image and place them back on the final nebulosity image using the PM formula: combine(nebulosity, stars,op_screen()).

Bruce

Comments

  • There isn't a difference. It is the same math in terms of screening in particular. The argument is, in the script it is convenient and avoids the pixel math expressions.
    -the Blockhead
  • Actually there are differences. 

    Adding and removing stars is usually best done at the linear stage but this is not always practical given the required workflow. The ScreenStars script gives the option to work on pseudo linear images by applying a reverse stretch to return the image to a pseudo linear state, then adding/removing stars, then stretching the image back to its original non-linear state. This can provide improved star colour, particular when the starless image has a very different colour palette from the image from which the stars were taken.

    Another difference is the maths used when the stars are "unscreened".  StarXTerminator does not use the standard unscreen formula. For example, if you unscreen using SXT and then screen back using combine(starless, stars, op_screen()), you will not get back to where you started - especially for the brighter stars. I understand that the RC-Astro maths is intended to provide some protection when an image has blown out nebulosity. If you don't have issues like this in your image then I would suggest the standard maths (as incorporated in ScreenStars) is to be preferred.

    I hope this helps
    CS, Mike
  • Oh,..that is right, I forgot about the reverse stretch thing. Thanks Mike.
    -the Blockhead
  • Hi Mike

    Yes- your response does help a lot.
    Thank You,
    Bruce
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