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I don't know of a good quality reducer that would get a RC8 down to f/4. The Astro-Physics CCDT67 is 0.67x and its big brother, the 27TVPH, is 0.75x. They are among the better reducers but won't give you a completely flat field with the RC design. You can also get a flattener which leaves the F ratio more or less unchanged.
With a newt you'll need a corrector unless you're using a very small sensor. Otherwise you'll get bad coma off axis.
Both options will work but the newt is probably better as a fast, medium focal length astrograph and the RC as a slower, longer focal length astrograph.
Cheers,
Rick.
Last edited by RickS; 11-06-2013 at 01:36 PM.
Reason: Put an apostrophe in the wrong place. I hate that!
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