Need for advice - strange bright stripes appear during M78 shooting - Forums

Topic starter

Feb 2, 2025

=MsoNormalDear forum,=MsoNormalduring shooting M87 suddenly some bright stripes that look like diffraction patterns appear in raw files. While having no problems in the eastern direction (picture 1) the effect emerges while approaching meridian. After reaching their maximum (picture 2) the stripes fade but do not disappear completely (picture 3). It’s only on the M78, other targets are not affected. The stripes are constantly parallel to the horizon and in the upper half (towards higher azimuth).=MsoNormalMight it be a close streetlamp in this direction that affects targets with low DEC? This effect would be new to me because I shot also low(er) DEC targets in the past without having this effect, however always with a DNB filter and never with an UV/IR Cut filter. The tube extension and dew cap are fully pulled out so that no direct light from the lamp should reach the aperture.=MsoNormalHas anyone experienced similar problems?=MsoNormalSetup:
110/660 refractor
1.0 field flattener
UV/IR cut L2
ZWO ASI 2600 MC Pro
ZWO ASI EFW

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andrea tasselli

Frequent contributor

Feb 2, 2025

Stray light into the scope is the more likely explanation. I get something like that even with a rather long dew shield in place.

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Scott Horton

Feb 3, 2025

andrea tasselli:
Stray light into the scope is the more likely explanation. I get something like that even with a rather long dew shield in place.

I agree, looks like stray light especially given the accompanied gradient.

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Julian Mochayedi

Feb 3, 2025

Hi Thomas,

I've experienced exactly the same thing for m78 with my Esprit 120 and asi2600. For me it was an unfortunate angle of object and near bright stars leading to extreme reflections inside the scope/equipment.

- Julian

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Tony Gondola

Frequent contributor

Feb 3, 2025

Is there an outside light source anywhere around. As others have mentioned it looks like stray light getting into your system.

Alex Roberts

Feb 3, 2025

Hi Thomas. I had the same light streaks, only worse. I believe it's glare from nearby Alnitak. Fortunately, although it was a lot of work, I was able to remove it in PixInsight with the CloneStamp tool, after removing the stars. You can see the end result here: https://www.astrobin.com/9agseh/

CS,

Alex

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Thomas

Topic starter

Feb 4, 2025

Dear all,
thanks for your contribution to tackle this issue. M78 seems to be a candidate for this observation. If nearby bright start (e.g. Alnitak) might be responsible for the stray light, why does the problem not emerge all night. Currently the phenomenon begins to occur at a certain altitude (close to meridian). Shouldn’t bright stars be distractive in general over entire night? CSThomas

andrea tasselli

Frequent contributor

Feb 4, 2025

I don't think it's a bright star off-field. They generate streaks, not bands. Your issue is with a light source relatively nearby.

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