Appendix F; Maksutov-Cassegrain Optical System - Meade EXT90 Instruction Manual

APPENDIX F:

MAKSUTOV-CASSEGRAIN OPTICAL SYSTEM

In the optical design of the ETX90, light enters from the
right through a multi-coated meniscus lens, proceeds to
an f/2.2 primary mirror, and then to a convex secondary
mirror that multiplies effective focal length by a factor of
6.3. The secondary mirror light baffle, in combination
with the anti-reflection threads inside the primary mirror
baffle, produces extremely high contrast astronomical
images at the focal plane. The oversize 96mm-diameter
primary mirror results in a fully-illuminated (unvignetted)
field of view significantly wider than can be obtained
with Maksutov optics incorporating primary mirrors of
the same apertures as their correcting lenses.