Quote:
Originally Posted by Peter.M
A smaller secondary for an astrograph would be a bad idea, I think that he is better off increasing the size of the secondary to "future proof" himself for when he hooks this beasty to a 11002 chip.
Also the 100% rays are all you need to worry about, vignetting of the 75% rays dont mean anything if you are fully illuminating the chip. If you are planning on constructing a tube for this a 13 inch diameter for a 12 inch scope is a little ambitious with the cell and room to tilt the mirror for collimation.
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Thanks Jay and Peter, I wasn't sure how big the tube should be around the mirror, I just put in 13" because it was bigger than 12"
The 88mm secondary is the one that comes in the GSO 12" f/4 kit, and it's the biggest they make. I think I'll happily continue playing with my DSLRs for now, a dedicated astro CCD isn't really on the horizon for me at the moment.
Would a bigger secondary move the focuser further down (shorten) the tube?