Orion Telescope Unpacking Your Scope, Attaching the Visual Back, Inserting a Star Diagonal

Congratulations on your purchase of an Orion Schmidt-Cassegrain telescope! The Schmidt-Cassegrain opti- 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.

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.

Finder scope

	Finder scope bracket
Visual back	Dovetail finder-scope base

Eyepiece

Diagonal

Focus knob

Figure 2. Rear cell

	Orion 8" SCT	Orion 9.25" SCT	Orion 11" SCT
Focal Length, Ratio	2032mm, f/10	2350mm, f/10	2800mm, f/10
Tube Material	Aluminum	Aluminum	Aluminum
Coatings	StarBright™ XLT	StarBright™ XLT	StarBright™ XLT
Highest Useful Magnification	480x	555x	660x
Secondary Mirror Obstruction	2.7"	3.35"	3.75"
-- By Area	11%	13%	12%
-- By Diameter	34%	36%	34%
Tube Length	17"	22"	24"
Tube Weight	12 lbs.	20 lbs.	27 lbs.

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