Orion Telescope User Manual

INSTRUCTION MANUAL

Orion

Schmidt-Cassegrain

Telescopes 8", 9.25", & 11"

Providing Exceptional Consumer Optical Products Since 1975

Customer Support ( 80 0) -6 76 -1 34 3 E-mail: suppor t@ te le sc op e. co m

Corpo rate Off ices (831) -763- 700 0

P.O. Box 1815, Santa Cruz, CA 95061

IN 265 Rev. A 8/05

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.

Eyepiece

Diagonal

Figure 2. Rear cell

Visual back

Focus knob

Finder scope

Finder scope bracket

Dovetail finder-scope base

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

Tube Weight

17" 22" 24"

12 lbs. 20 lbs. 27 lbs.

Inserting an Eyepiece

Aligning the Finder Scope

An eyepiece magnifies the image focused by the telescope. The eyepiece fits into either the visual back directly or the star diagonal. To install an eyepiece:

1. Loosen the set screw on the star diagonal until the tip no longer extends into the inner diameter of the eyepiece end of the diagonal.

2. Slide the chrome portion of the eyepiece into the star diag onal.

3. Tighten the set screw on the star diagonal to hold the eye piece in place.

To remove the eyepiece, loosen the setscrew on the star diagonal and slide the eyepiece out. You can replace it with another eyepiece (purchased separately).

Eyepieces are commonly referred to by focal length and bar rel diameter. The focal length of each eyepiece is printed on the eyepiece barrel. The longer the focal length (i.e., the larger the number) the lower the eyepiece magnification, the shorter the focal length (i.e., the smaller the number) the higher the magnification. Generally, you will use low to moderate pow ers when viewing. For more information on how to determine power, see the section on “Calculating Magnification.”

Attaching a Finder Scope

A finder scope is a small, wide-field telescope used to help locate and center objects in the field of your main telescope. The finder scope has a built-in crosshair reticle that shows the optical center of the finder’s field of view.

1. To install an Orion finder scope, you must first attach a dovetail finder scope base (#7215) to the telescope. Line up the through-holes in the base with the threaded holes in the rear cell of the telescope tube. Then insert the two supplied screws through the base and thread them into the telescope holes until secure (Figure 3a). Now you’re ready to attach the finder scope.

2. Unthread the two black nylon thumbscrews until the ends are flush with the inside of the bracket (Figure 3b). Remove the O-ring from the foot of the bracket and slide it over the back of the finder (it will NOT fit over the objective end of the finder). It may need to be stretched a little. Slide it until it seats into the slot in the middle of the finder tube.

3. Slide the eyepiece end (narrow end) of the finder scope into the end of the bracket’s cylinder opposite the align ment screws while pulling the chrome, spring-loaded ten sioner pin on the bracket with your fingers (Figure 3c).

Push the finder scope through the bracket until the O-ring

seats just inside the front opening of the bracket cylinder. Release the tensioner pin and tighten the two black nylon thumbscrews a couple of turns each to secure the finder scope in place.

4. Now inser t the foot of the finder scope bracket into the dovetail base. Lock the bracket into position by tightening the knurled thumbscrew on the dovetail holder.

Accurate alignment of the finder scope makes it easy to find objects with the telescope, especially celestial objects. To make aligning the finder as easy as possible, this proce dure should be done in the daytime when it is easy to find and identify objects. The finder scope has two perpendicular adjustment screws and a spring-loaded pin that allow easy adjustment of the finder scope horizontally and vertically. To

align the finder:

Figure 3a. Attaching the optional dovetail finder scope base.

Alignment

Focus lock ring

Objective lens

Figure 3b. The Orion 6x30 finder scope.

thumbscrews

Finder-scope

Figure 3c.

Pull the springloaded tensioner outward, then insert the finder scope into the finder scope bracket.

Eyepiece

Tensioner

bracket

Dovetail

foot

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