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Congratulations on your purchase of an Orion Schmidt-Cassegrain telescope!
cal system uses a combination of mirrors and lenses and is referred to as a compound or catadioptric telescope. This unique
design offers large-diameter optics while maintaining very short tube lengths, making them extremely portable and versatile. The
Schmidt-Cassegrain system consists of a zero-power corrector plate, a spherical primary mirror, and a secondary mirror. Once
light rays enter the optical system, they travel the length of the optical tube three times, exiting through a hole in the center of the
primary mirror to the eyepiece.
Orion-brand Schmidt-Cassegrain tube assemblies are made by Celestron International in the U.S.A. The optics feature
Starbright® XLT coatings -- enhanced multi-layer coatings on the primary and secondary mirrors for increased reflectivity and a
fully coated corrector for the finest anti-reflection characteristics.
Unpacking Your Scope
Use case when unpacking the shipping carton. We recom-
mend keeping the boxes and all original packaging materi-
als. In the event that the telescope needs to be shipped to
another location, or returned for warranty repair, having the
proper packaging will ensure that your telescope will survive
the journey intact. Returns for refund or exchange will not be
accepted without the original packaging.
Figure 1.
Cutaway view of the light path of the
Schmidt-Cassegrain optical design.
Attaching the Visual Back
The visual back is the accessory that allows you to attach all
visual accessories to the telescope. The optical tube should
come with the visual back installed. If it is not already on the
tube it can be attached as follows:
1. Remove the rubber cover on the rear cell.
2. Place the knurled slip ring on the visual back over the
threads on the rear cell (Fig 2).
3. Hold the visual back with the set screw in a convenient
position and rotate the knurled slip ring clockwise until
tight.
Once this is done, you are ready to attach other accessories,
such as a diagonal prism and eyepiece.
To remove the visual back, rotate the slip ring counterclock-
wise until it is free of the rear cell.
Focal Length, Ratio
Tube Material
Coatings
Highest Useful Magnification
Secondary Mirror Obstruction
-- By Area
-- By Diameter
Tube Length
Tube Weight
2
Inserting a Star Diagonal
A star diagonal is a prism that diverts the light at a right angle
to the light path of the telescope. This allows you to observe
in positions that are physically more comfortable than if you
looked straight through the scope.
To insert a star diagonal:
1. Turn the set screw on the visual back until its tip no lon-
ger extends into (i.e., obstructs) the inner diameter of the
visual back.
2. Slide the chrome portion of the star diagonal into the visu-
al back.
Tighten the set screw on the visual back to hold the star diag-
onal in place.
Eyepiece
Diagonal
Figure 2.
Orion 8" SCT
Orion 9.25" SCT
2032mm, f/10
2350mm, f/10
Aluminum
StarBright
XLT
StarBright
™
480x
2.7"
11%
34%
17"
12 lbs.
The Schmidt-Cassegrain opti-
Finder scope
Visual back
Focus knob
Rear cell
Orion 11" SCT
2800mm, f/10
Aluminum
Aluminum
XLT
StarBright
™
555x
3.35"
13%
36%
22"
20 lbs.
27 lbs.
Finder scope bracket
Dovetail finder-scope base
XLT
™
660x
3.75"
12%
34%
24"
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