Orion 120 EQ Terrestrial Viewing, Care and Maintenance, Specifications, Cleaning the Optics

Deep-sky objects are quite faint, and typically require expo- sures on the order of 10 minutes. To hold the camera’s shutter open this long, you will need a locking shutter release cable (#5231). Set the camera’s shutter to the “B” (bulb) setting. Depress the locking shutter release cable and lock it. You are now exposing your first deep-sky object.

While exposing through the camera lens, you will need to mon- itor the accuracy of the mount’s tracking by looking through the illuminated reticle eyepiece in the main telescope. If the guide star drifts from its initial position, then use the hand controller of the motor drive to “move” the guide star back to the center of the crosshairs. Any drifting along the Dec. axis is a result of improper polar alignment, so if the guide star drifts greatly in Dec., the mount may need to be polar aligned more accurately.

When the exposure is complete, unlock the shutter release cable and close the camera’s shutter.

Astrophotography can be enjoyable and rewarding, as well as frustrating and time-consuming. Start slowly and consult out- side resources, such as books and magazines, for more details about astrophotography. Remember...have fun!

8. Terrestrial Viewing

The AstroView 120 Refractor may also be used for long-distance viewing over land. For this application we recommend substitution of an Orion 45° Correct-Image Diagonal (#8790) for the 90° star diagonal that comes standard with the telescope. The correct- image diagonal will yield an upright, nonreversed image and also provides a more comfortable viewing angle, since the telescope will be aimed more horizontally for terrestrial subjects.

For terrestrial viewing, it’s best to stick with low powers of 50x or less. At higher powers the image loses sharpness and clar- ity. That’s because when the scope is pointed near the horizon, it is peering through the thickest and most turbulent part of the Earth’s atmosphere.

Remember to aim well clear of the Sun, unless the front of the telescope is fitted with a professionally made solar filter and the finder scope is covered with foil or some other completely opaque material.

9. Care and Maintenance

If you give your telescope reasonable care, it will last a life- time. Store it in a clean, dry, dust-free place, safe from rapid changes in temperature and humidity. Do not store the tele- scope outdoors, although storage in a garage or shed is OK. Small components like eyepieces and other accessories should be kept in a protective box or storage case. Keep the cap on the front of the telescope when it is not in use.

Your AstroView 120 telescope requires very little mechanical maintenance. The optical tube is aluminum and has a smooth painted finish that is fairly scratch-resistant. If a scratch does appear on the tube, it will not harm the telescope. If you wish, you may apply some auto touch-up paint to the scratch. Smudges on the tube can be wiped off with a soft cloth and a household cleaner such as Windex or Formula 409.

Cleaning the Optics

A small amount of dust or a few specks on the glass objective (main) lens will not affect the performance of the telescope. If dust builds up, however, simply blow it off with a blower bulb, or lightly brush it off with a soft camel hair brush. Avoid touching optical sur- faces with your fingers, as skin oil may etch optical coatings.

To remove fingerprints or smudges from a lens, use photo- graphic-type lens cleaning fluid and lint-free optical lens cleaning tissue. Do not use household cleaners or eyeglass- type cleaning cloth or wipes, as they often contain undesirable additives like silicone, which don’t work well on precision optics. Place a few drops of fluid on the tissue (not directly on the lens), wipe gently, then remove the fluid with a dry tissue or two. Do not “polish” or rub hard when cleaning the lens, as this will scratch it. The tissue may leave fibers on the lens, but this is not a problem; they can be blown off with a blower bulb.

Never disassemble the telescope or eyepieces to clean opti- cal surfaces!

10. Specifications

Optical tube: Seamless aluminum

Objective lens diameter: 120mm (4.7")

Objective lens: crown and flint, achromatic, air-spaced, dif- fraction limited

Objective lens coating: fully coated with multi-coatings

Focal length: 1000mm

Focal ratio: f/8.3

Eyepieces: 25mm and 10mm Plössls, fully coated, 1.25"

Magnification: 40x (with 25mm), 100x (with 10mm)

Focuser: Rack and pinion, accepts 1.25" or 2" accessories

Diagonal: 90° star diagonal, mirror type, 1.25"

Finder scope: 6x magnification, 30mm aperture, achromatic, crosshairs

Mount: German-type equatorial

Tripod: Aluminum

Motor drives: Optional

15