Quote:
Originally Posted by peter_4059
Thanks for that tip Rick. How do you determine how many/what size stars need to be masked? Also in linear processing steps should the mask be STF stretched when comparing to the image?
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Hi Peter,
The coverage I look for depends on what I'm trying to achieve. A mask to use as a decon ringing support only needs the very largest stars, so linear data with a small midtones stretch works well. A star mask to use for blurring chrominance (helpful to make star cores more colourful) only needs the large and middle sizes stars. A mask for star size reduction or star removal usually includes stars of all sizes. For this, Colin's suggestion of combining multiple masks with the PixelMath max() function is useful.
You can stretch a star mask and I do this occasionally especially when combining multiple masks, perhaps to strengthen the masking of smaller stars. You don't usually need to stretch a star mask just because it is based on or being applied to linear data.
A star mask is just an image so you can apply any PI process or script to it. I often use MorphologicalTransformation Erosion or Dilation to adjust a mask.
Applying HDRMT with a very heavy hand (say 4 or more iterations) is often a good way to pre-process a copy of an image before running StarMask, especially if there are stars buried in nebulosity.
Cheers,
Rick.