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Halo with narrow band filter

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#1 palamrinder

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Posted 19 January 2021 - 02:13 PM

I recently started using STC dual narrowband clip in filter on my Fuji camera. I realized there was slight halo around the center of the frame. I was checking the flat frames and could see a faint black circle in the middle with light halo around it. Exacerbated it with tone curve. Any ideas what could be causing this? It shows up after stacking the pictures. Attaching the blue picture with filter on the camera (shot with Fuji 55-200mm lens at 200mm, 2 minute exposure) and the yellow picture without the filter from few weeks ago (using Fuji 100-400mm at 400mm for 30 seconds). Both shots taken with Fuji XT30 at ISO 3200.

 You can also see that halo around Orion Nebula picture I took with this filter (taken with 100-400mm at 400mm with 30 second exposures)

Attached Thumbnails

  • STC filter.jpg
  • no filter.jpg
  • orion halo.jpg

Edited by palamrinder, 19 January 2021 - 02:15 PM.


#2 Rasfahan

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Posted 19 January 2021 - 04:37 PM

That is due to an internal reflection. It is cause by a reflection between some glass element and the filter. I can offer no help about how to resolve it for a camera/lens system since you cannot change the distance of the glass pieces. I have a similar (though not as bad) issue with my O3 filter (with *any* scope/camera combination) and have not been able to resolve it. I have it in lights and flats. If you only have it in your flats, try retaking the flats in different lighting circumstances. If you have them in flats and lights, you might try to modify your flats (i. e. multiply them with a constant or add a constant to all pixel values) and try to get them to correctly correct, this can mitigate the problem.



#3 palamrinder

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Posted 25 January 2021 - 02:56 PM

That is due to an internal reflection. It is cause by a reflection between some glass element and the filter. I can offer no help about how to resolve it for a camera/lens system since you cannot change the distance of the glass pieces. I have a similar (though not as bad) issue with my O3 filter (with *any* scope/camera combination) and have not been able to resolve it. I have it in lights and flats. If you only have it in your flats, try retaking the flats in different lighting circumstances. If you have them in flats and lights, you might try to modify your flats (i. e. multiply them with a constant or add a constant to all pixel values) and try to get them to correctly correct, this can mitigate the problem.

Thanks. Fortunately this only happens with one of the lenses. I didn't see this with another lens and will try to use that one more often.




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