View Single Post
  #4 (permalink)  
Old 28-April-2008, 03:22 PM
RickJ RickJ is online now
Senior Member
 
Join Date: Dec 2006
Location: Mantrap Lake, MN
Posts: 853
Default

Note that while RC scopes have far less coma and a somewhat flatter field than standard cassegrains the field isn't totally coma free as there's 5th order coma. Also there's an astimatism problem that can crop up. For large fields you do need a flattener. It has to be specific to the scope as well. See: http://www.rcopticalsystems.com/redcorr.html

They are easier to correct than a standard cassegrain or newtonian or even Meade's so called RC like system. With say an ST-10 there's no need for any correction but with today's super large CCD's or medium format film you'd want a corrector.

I find nothing on this new line on Astronomic's website. Most chinese optics I've seen are good but not great. Most mirrors seem to have a zonal problem that while small would scatter light for astrophotographic purposes looking like poorer seeing than there really was. Mechanics are highly important in RC systems and part of the high cost. I'd worry those aren't up to snuff as well. I suspect they'll be about the overall quality of Meade's modified SCT's rather than RC Optical System's or Star instrument's quality. Good but not great. The lack of a corrector plate and its blue chromatic abberation would give it a slight advantage over Meade's scope if the rest of it is up to snuff.

I'd say "interesting but show me" is my attitude for now.

Rick
Reply With Quote