Back to forums

Looking for advice on removing vertical streaks in my Blue channel (M45)

Pleiades Astrophoto PixInsight Calibration Artifacts M45 Troubleshooting
3 replies•62 views
Miles B avatar
Miles B avatar

Hey everyone,

I’m running into a calibration/processing issue with my Blue channel on M45 and could use some help from people who’ve seen this before.

My B-subs are showing strong vertical streaks coming off the brightest stars (example frame attached). When I process the data in PixInsight, those streaks turn into dark blue lines across the stars after channel combination and color calibration. They’re very noticeable in the final image and I haven’t found a reliable workflow to reduce or remove them.

My setup:

  • William Optics GT71

  • ZWO ASI2600MM Pro

  • Baader Blue filter (this is an LRGB image, but only the images with blue filter contain the streaks)

  • Exposures: 180s, Gain 100, –10°C

  • ~4.5 hours collected in B

  • Flats + dark flats + darks were taken

  • Guiding was consistent (0.5–0.7 RMS)

What I’ve tried in PixInsight:

  • Large-scale rejection in ImageIntegration

  • NoiseXTerminator

  • StarXTerminator + recomposition

Questions for anyone who has dealt with this:

  1. Can these be fixed in processing, or is this a calibration mismatch problem?

  2. What’s the best PixInsight workflow to suppress these without destroying star color?

Any advice, workflows, or comparisons would be really appreciated.

Thanks in advance!IMG_8958.jpeg

Well Written Engaging
andrea tasselli avatar
andrea tasselli avatar
You have very bad field curvature and what you see is a side dish of that coupled with a refractor being a refractor. I can't think of anything that can potentially help you out here. It's a case of fix it and try again, I'm afraid.
Miles B avatar
Miles B avatar

andrea tasselli · Nov 28, 2025 at 01:34 PM

You have very bad field curvature and what you see is a side dish of that coupled with a refractor being a refractor. I can't think of anything that can potentially help you out here. It's a case of fix it and try again, I'm afraid.

Thank you, Andrea! I appreciate the insights.

I’ll definitely look into spacing and tilt to clean up the star shapes in the corners.

One thing I’m still trying to understand better: the streaks only appear in the Blue channel, not in R or G. Does field curvature typically cause channel-specific artifacts? I was wondering if this might be something else (calibration, microlens effects, etc.)

Any thoughts are appreciated!

Well Written Respectful Engaging
andrea tasselli avatar
andrea tasselli avatar
It is something very much to do with the refractive characteristic of your glass, which vary quite a bit at different wavelengths so no surprise the B channel is affected and the others don't. It could be a case of birefringence. Some times this happens because of pre-existing strains in the glass get worse with the cold weather. I don't think it is anything to do with your processing.