Leisure Time LX20 - Manual (Page 2)

In the Schmidt-Cassegrain design of the Meade 8", 10", and 12" models, light enters from the right, passes through a thin lens with 2-sided
aspheric correction ("correcting plate"), proceeds to a spherical primary mirror, and then to a convex aspheric secondary mirror. The
convex secondary mirror multiplies the effective focal length of the primary mirror and results in a focus at the focal plane, with light passing
through a central perforation in the primary mirror.
The 8", 10", and 12" models include oversize 8.25", 10.375" and 12.375" primary mirrors, respectively, yielding fully illuminated fields-of-
view significantly wider than is possible with standard-size primary mirrors. Note that light ray (2) in the figure would be lost entirely, except
for the oversize primary. It is this phenomenon which results in Meade 8", 10", and 12" Schmidt-Cassegrains having off-axis field
illuminations 10% greater, aperture-for-aperture, than other Schmidt-Cassegrains utilizing standard-size primary mirrors. The optical
design of the 4" Model 2045D is almost identical but does not include an oversize primary, since the effect in this case is small.
LX200 Schmidt-Cassegrain telescopes now feature new baffle tube designs. These computer-optimized designs incorporate a series of 7
to 11 (depending on the focal ratio and size of the LX200) internal field-stops to eliminate almost all internal reflections, yielding the best
image contrast available in any Schmidt-Cassegrain available today.
The Meade 7" Maksutov-Cassegrain Optical System (Diagram not to scale)
The Meade 7" Maksutov-Cassegrain design optimizes imaging performance by utilizing a combination of two-sided spherical meniscus
lens (right), a strongly aspheric f/2.5 primary mirror, and a spherical secondary mirror. The convex secondary mirror multiplies the
effective focal length of the primary by a factor of six, resulting in an overall f/15 system at the Cassegrain focus.
The oversize 8.25" 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 aperture as their meniscus correcting lenses. Computer-optimized primary and
secondary mirror baffles, as well as a sequence of field stops internal to the primary mirror baffle, yield lunar, planetary, stellar, and deep-
space images of uncommonly high contrast and resolution.
NOTE: Instructions for the use of optional accessories
are not included in this manual. For details in this regard,
see the Meade General Catalog.