Meade 2080 - Page 3

NOTE
Instructions for the use of the following optional
accessories and systems are not included in this
manual, but are shipped with the respective items:
Table Tripod for Model 2080
Model 46 VariGuide Dual-Axis Drive Corrector
Models 2047, 2048 4" Schmidt-Cassegrain Photo-Guide
Telescopes
Models 2066, 2068 4" f/2.64 Schmidt Cameras
Models 41 and 43 R.A. Drive Correctors
THE SYSTEM 2000 SCHMIm:cASSEGAAlN OPTICAL SYSTEM
(Diagram not to scale.)
F
(2)
In the Schmidt-Cassegrain design of the Meade &-inch
Model 2080 shown. tight enters from the right. passes
through a thin lens with 2-stded aspheric correction (1)
rcorrecting plate1. proceeds to a spherical primary (2)
and then to a convex aspheric secondary mirror (3). The
convex secondary mirror multiplies the effective focal
length of the primary mirror and results in a focus at F.
with light passing through a central perforation in the
primary mirror.
The 8-inch Mode12080 telescope includes an over-
size 8.25-inch diameter primary mirror. yielding a fulty it.
luminated fieId-of-view significantly wider than is possible
with a standard 8-inch diameter primary. Because the
Schmidt correcting plate near its edge acts. in effect. as a
negative lens. ighI impinging near the circurnferenceof the
correcting plate is lost unless the primary mirror size c0m-
pensates for this light diverging from the corrector. (Note in
the diagram lhallight rays A1and A2would be lost except
for the oversize primary mirror.) In fact. the oversize primary
of the Model 2080 results in about 6 percent more &ght
reaching the focal surface of the telescope. The optical
design of the 4. Model 2040 is almost identical but does not
include an oversize primary. since the effect in this case is
small.