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Old 23-07-2009, 10:46 AM
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pmrid (Peter)
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Is this a Ritchey-Chretien thing, or a Canon 1000D thing?

I'd be greteful for suggestions about causes and cures for this artifact I am getting in recent images with a new 8" GSO RC. The centre of the image seems to bloom with a fog of light. I have also seen those damned elliptical halos of light from bright stars just on the edge or just off the edge of an image but that seems to be something different and is probably related tp internal reflections.
Here are 2 recent images and you'll see the light blook in the central image. I am hoping more experienced RC users will see this and be able to make an easy diagnosis and presecribe a cure.

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Old 23-07-2009, 11:46 AM
Hagar (Doug)
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Hi Peter, you seem to have 2 problems here. Both are fixable. The first, the light bloom in the centre is caused usually by uneven illumination of the CCD. Flat frame calibration will usually fix this without too many problems. The only other fix and I doubt this is possible is a bigger baffle tube and focuser.
The second problem is a reflection problem assosiated with the main baffle tube and is fixable with flocking of the baffle tube.

These problems/ aberations are fairly normal for most RC/SC scopes with 2" focusers and 2" baffle tubes.

I hope this helps.

Last edited by Hagar; 23-07-2009 at 09:32 PM.
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Old 23-07-2009, 03:05 PM
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Tandum (Robin)
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Peter, I'll have my 8" light box there on Saturday, you can snap a few flats with it.
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