Orion 9874 instruction manual Specifications

The large primary mirror and the elliptical secondary mirror of your telescope are front-surface aluminized and over-coated with hard silicon dioxide, which prevents the aluminum from oxidizing. These coatings normally last through many years of use before requiring re-coating (which is easily done).

To clean the secondary mirror, first remove it from the tele‑ scope. Do this by holding the secondary mirror holder station‑ ary while turning the center Phillips-head screw. Be careful, there is a spring between the secondary mirror holder and the Philips-head screw; be sure that it will not fall into the optical tube and hit the primary mirror. Handle the mirror by its hold‑ er; do not touch the mirror surface. Then follow the same pro‑ cedure described below for cleaning the primary mirror. You do not need to remove the secondary mirror from its holder when cleaning.

To clean the primary mirror, carefully remove the mirror cell from the telescope. To do this means you must remove the six screws on the side of the tube near the primary mirror. You do not need to remove the collimation screws on the bottom of the mirror cell. Remove the mirror cell from the tube. You will notice the primary mirror is held down with four clips held by two screws each. Loosen the screws and remove the clips.

You may now remove the mirror from the mirror cell. Do not touch the surface of the mirror with your fingers. Lift the mirror carefully by the edges. Set the mirror on a clean soft towel. Fill a clean sink free of abrasive cleanser, with room-tempera‑ture water, a few drops of liquid dishwashing detergent, and if possible, a capful of rubbing alcohol. Submerge the mirror (aluminized face up) in the water and let it soak for a few min‑ utes (or hours if it’s a very dirty mirror). Wipe the mirror under water with clean cotton balls, using extremely light pressure and stroking in straight line across the mirror. Use one ball for each wipe across the mirror. Then rinse the mirror under a stream of lukewarm water. Any particles on the surface can be swabbed gently with a series of cotton balls, each used just one time. Dry the mirror in a stream of air (a “blower bulb” works great), or remove any stray drops of water with the corner of a paper towel. Water will run off a clean surface. Cover the mirror surface with Kleenex, and leave the mirror in a warm area until it is completely dry before reassembling the telescope.

11. Specifications

Primary mirror diameter: 254mm

Primary mirror coating: Aluminized, SiO2 overcoat

Primary mirror material: Pyrex®

Focal length: 1200mm

Focal ratio: f/4.7

Secondary mirror axis: 64mm

Secondary mirror holder: Four-vaned spider

Eyepiece: 25mm and 10mm Sirius Plössls, fully coated, 1.25"

Magnification: 48x (with 25mm) and 120x (10mm)

Finder scope: 9x50 achromatic, 5° field of view

Focuser: Rack and pinion, push-pull tilt adjustment for collimating, accepts 2" and 1.25" eyepieces

Camera adapter: couples 35mm SLR camera T-Ring to focuser

Mount: Atlas, German equatorial

Tripod: Steel

Tripod support tray: Aluminum, provides additional stability, holds five 1.25" eyepeices and two 2" eyepieces

Weight: 54 lbs.

Counterweights: Quantity 3, 11 lbs. each

Setting circles: R.A. scaled in 10 min. increments, Dec. scaled in 2° increments for N or S hemisphere

Polar axis latitude adjustment: 10° to 65°

Polar axis finder scope: Included

Motor drives: Dual-axis, internally housed

Power requirements: 12V DC, tip positive

Battery type: Eight D-cells

Operation: Northern or Southern hemisphere

Guiding rates: Sidereal ±100% sidereal

Centering rates: ±8x sidereal, ±16x sidereal

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