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Artifacts from reflected light

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#1 AJS1

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Posted 22 October 2021 - 01:01 PM

I have an Explore Scientific ED 127 FCD 100 Scope. When a bright object is located just outside the field of view I get a arc shaped artifact across my image. These are large (about 2/3 the height of the sensor) which would seem to indicate that they originate a long way from the sensor. maybe at or near the objective lens. They only occur when a bright object is located just outside the field of view. If there is no bright object then there is no arc shaped artifact. Has anyone experienced this with this or any other refracting telescope. I can process them out with PS but it is a pain. Your thoughts would be appreciated.



#2 sharkmelley

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Posted 22 October 2021 - 01:18 PM

It's a common problem.  The light from a star outside the field of view (of the sensor) can reflect off internal circular/cylindrical surfaces and generate the arc.  The problem is finding which reflective surface is the culprit.  A dew shield can often help by masking the light from those stars.



#3 AJS1

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Posted 22 October 2021 - 01:52 PM

Thanks Sharkmelley. Could the reflective surface be the edge of the objective lens?



#4 sharkmelley

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Posted 23 October 2021 - 12:03 AM

Thanks Sharkmelley. Could the reflective surface be the edge of the objective lens?

No.  That would not arrive at the sensor focused into an arc.  It will be caused by something much nearer the camera such as focuser tube, reducer, extension tube, camera adapter, filter edge etc.

 

Mark




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