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Hi everyone! There is a known issue with Celestron EdgeHD scopes: a nearby bright star produces rays of scattered light. It looks like this:  Little Dipper - An Asterism in Perseus According to my measurements a bright star should be approximately from 27 to 35 acrmins from the center of the field of view to produce this effect in EdgeHD 11 scope. Here is an animation of frames (full frame sensor) where a 2m star Mirach is positioned from 21 to 35 arcmins from the FOV center. As you can see, frames at 29, 31 and 33 arcmins are affected:  And the same frames in a column:  I hope that this will be helpful. I take this into account when I frame targets and try to make sure that no bright stars are located in the "bad" range. CS, Vitali |
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Thanks for info, Vitali! CS! |
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This problem dissapeares by using a dew cap very nicely. Cheers, Christoph |
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Indeed, I always use a dew cap and have not encountered that issue so far. Cheers, Stefan |
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Christoph Lichtblau: Stefan: I've forgot to mention that my scope has an Astrozap aluminium dew cap (AZ-256). |
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Vitali: That‘s interesting. I use an APS-C sized sensor not a full frame. Perhaps that is part of the story. |
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Stefan: Actually you are right. I did not notice this issue with my old ASI071MC camera which has APS-C sensor. Now I use a full frame ASI2400 and these rays became visible. |
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| It's not tied to the EdgeHD specifically. I've had the same thing happen with my William Optics GT81 and ASI6200MM. I'm wanting to say it was Deneb when I was shooting the North American Nebula and Pelican Nebula. I suspect it's tied to sensor size and what the image circle from the scope is plus how far out of frame the bright star is. I had a momentary panic that my at the time new ASI6200MM was dying. |
