Meade ETX-90 User Manual - Page 55

Optical Systems

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OPTICAL SYSTEMS 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. 55

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MAKSUTOV-CASSEGRAIN OPTICAL SYSTEM
APPENDIX F:
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.
OPTICAL SYSTEMS
²²