Pixinsight: No FWHM values on ImageIntegration to control stars' size on OSC camera.

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Apostolos Kyriazis avatar

I am working on an image of B228 (camera: 533MC) and I have almost 120 frames of 300’’ with a simple Uv/Ir cut filter.

On Pixinsight, when I try to separate stars and nebulosity through StarXterminator so I can work on them separately, 3 stars still remain on the starless image (despite their good size and shape). So when i work on its curves, those stars get inevitably pumped up as well.

I was hoping that on ImageIntegration, I could set up a weight limit on the FWHM value, to control the star size and get rid of the large ones. Theoretically, this could help me decrease the stars’ size overall and cut them off the starless version.

However, even though the SubFrameSelector function counts the FWHM values, the ImageIntegration function does NOT have FWHM as an option.

The only alternative I see left is to note down the images with a large FWHM and manually exclude them from the Integration.

Any other ideas?

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Scott Badger avatar

You can enter a filter expression in the SFS Expressions/Approval panel: FWHM < X, or an FWHM based weight formula (plus any other factors like eccentricity or number of stars) in the weighting section if you don’t want to toss the subs completely. Give it a keyword like SWEIGHT and use the FITS Keyword option in ImageIntegration/weighting.

Cheers,

Scott

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Apostolos Kyriazis avatar

Scott Badger · May 31, 2026, 07:11 PM

You can enter a filter expression in the SFS Expressions/Approval panel: FWHM < X, or an FWHM based weight formula (plus any other factors like eccentricity or number of stars) in the weighting section if you don’t want to toss the subs completely. Give it a keyword like SWEIGHT and use the FITS Keyword option in ImageIntegration/weighting.

Cheers,

Scott

Thank you! I will give it a try.