Old 06-11-2012, 07:56 PM
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graham.hobart (Graham stevens)

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Location: hobart, tasmania
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vignetting school boy error

Hey ho, I have a new ccd cam (QSI) with 1.25" filters in internal filter wheel. Tonight was taking flats on Tak TSA 120 with optec focuser (>2" focuser) using camera's 2" adaptor. And I wondered why my flats all looked like a globular cluster! Central portion lovely and illuminated, but that's it.
So apart from using a 1.25" adaptor, what can I do about it?
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Old 08-11-2012, 06:25 PM
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blink138 (Pat)
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Join Date: Aug 2009
Location: perth w.a.
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hey ho graham....... obviously not a schoolboy error eh!
not long posted a thread wondering how i could rid myself of vignetting using an f6.3 reducer on my c11 and 60da
as terry has pointed out if the image circle from your telescope, in my case the aperture (when you take off the visual back), say 40mm multiplied by the reducer (0.63) gives an image circle of about 23mm!
in my case my sensors diagonal is more than that so i get vignetting!
makes sense but dont know if it applies to your system...... sorry if it doesnt, but i certainly learned something simple
oh by the way the reducer has to be within thespecified distance from the chip
good luck
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