User Manual
49
LX65 OPTICAL SYSTEMS
APPENDIX D:
Unlike Schmidt-Cassegrain systems, Meade’s
Advanced Coma-Free (ACF) optical system provides
razor-sharp pin-point star images all the way to the
veryedgeoftheeldofview.Thisaplanatic(coma-
free) optical system brings the highest level of
performance to the amateur astronomer.
In the ACF design of the Meade LX65 telescope,
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 hyperbolic secondary mirror. The hyperbolic
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.
All models of the Meade ACF includes oversize
primary mirrors, yielding a fully illuminated eld-
of-view signicantly wider than is possible with a
standard-size primary mirror. Note that light ray (2)
in the gure would be lost entirely, except for the
oversize primary. It is this phenomenon which results
in Meade ACF having off-axis eld illuminations
about 10% greater, aperture-for-aperture, than other
systems utilizing standard-size primary mirrors. Field
stops machined into the inside-diameter surface of
theprimarymirrorbafetubesignicantlyincrease
lunar, planetary, and deep-space image contrast.
Theseeldstopseffectivelyblockoff-axisstraylight
rays.
In the Maksutov-Cassegrain design of the Meade
LX65, 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 bafe, in combination
with the anti-reection threads inside the primary
mirror bafe, produces extremely high contrast
astronomical images at the focal plane.
Primary Baffle Tube
Field Stops
Primary Mirror
Ray (1)
Ray (2)
(2)
(1)
(2)
(1)
Secondary
Mirror
Correcting
Plate
Secondary
Baffle
(2)
(1)
Focal
Plane
Primary Baffle Tube
Field Stops
Primary Mirror
Ray (1)
Ray (2)
(2)
(1)
(2)
(1)
Secondary
Mirror
Correcting
Plate
Secondary
Baffle
(2)
(1)
Focal
Plane
The Meade Advanced Coma-Free Optical System
The Meade Maksutov-Cassegrain Optical System
Aperture
Primary mirror
Secondary mirror
Focal point
Incident Light
PrimaryBafe
Meniscus Corrector Lens