An RC does not need a corrector for a flat field but it does "need" a flattener for field curvature to make the stars smaller at the corners.
How much it needs this perhaps depends on the model. The difference on an RCOS 12.5 inch I believe was marginal and not important.
That scope would evenly illuminate a STL11. RCs do not require correctors you may be thinking of corrected Dall Kirkhams which do and they are similar to an RC except I think its an ellipsoid primary mirror.
Planewave CDK and Orion Optics ODK are corrected Dall Kirkhams. So is the Ceravolo Astrograph. It seems to be the current popular design.
Greg.
Quote:
Originally Posted by White Rabbit
Hi Duncan.
Getting the itch...again...your worse than me mate. How many scopes is that weve seen you buy over the last year lol.
I thought, and I'm probably wrong, that coma and vignetting were both caused by the parabolic nature of the mirror/lense and the an RC design provides the flatest fied possible with todays (amature) scopes. Even though the RC has a parabolic mirror there is a corrector in there somewhere?
Thanks
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