User manual ORION TELESCOPES & BINOCULARS REV C 9024 AV 90EQ

[. . . ] INSTRUCTION MANUAL Orion® AstroViewTM 90mm EQ #9024 Equatorial Refracting Telescope Customer Support (800) 676-1343 E-mail: support@telescope. com Corporate Offices (831) 763-7000 Providing Exceptional Consumer Optical Products Since 1975 P. O. Box 1815, Santa Cruz, CA 95061 IN 112 Rev. C 05/02 Piggyback camera adapter Tube mounting rings Finder scope bracket Tube ring mounting plate Dec. slow-motion control Counterweight lock knob Counterweight shaft Counterweight Latitude locking T-bolt Azimuth lock knob Latitude adjustment T-bolt Alignment screws (2) Eyepiece Star diagonal Focus knob Dec. [. . . ] The key things to remember when pointing the telescope are, first that you only move it in R. A. and Dec. , not in azimuth or latitude (altitude), and second, the counterweight and shaft will not always appear as it does in Figure 1. In fact, it almost never will! Beware, too, that nearby porch lights, streetlights, and car headlights will ruin your night vision. Aiming the Telescope To view an object in the main telescope, first loosen both the R. A. Aim the telescope at the object you wish to observe by "eyeballing" along the length of the telescope tube (or use the setting circles to "dial in" the object's coordinates). Then look through the (aligned) finder scope and move the telescope tube until the object is generally centered on the finder's crosshairs. Then accurately center the object on the finder's crosshairs using the R. A. The object should now be visible in the main telescope with a low-power (long focal length) eyepiece. slow-motion controls to reposition the object within the field of view of the main telescope's eyepiece. Focusing the Telescope Practice focusing the telescope in the daytime before using it for the first time at night. Start by turning the focus knob until the focuser drawtube is near the center of its adjustment range. Insert the star diagonal into the focuser drawtube and an eyepiece into the star diagonal (secure with the thumbscrews). Point the telescope at a distant subject and center it in the field of view. Now, slowly rotate the focus knob until the object comes into sharp focus. Go a little bit beyond sharp focus until the image just starts to blur again, then reverse the rotation of the knob, just to make sure you hit the exact focus point. The telescope can only focus on objects at least 50 to 100 feet away. If you wear eyeglasses, you may be able to keep them on while you observe, if your eyepieces have enough "eye relief" to allow you to see the whole field of view. You can try this by looking through the eyepiece first with your glasses on and then with them off, and see if the glasses restrict the view to only a portion of the full field. If they do, you can easily observe with your glasses off by just refocusing the telescope the needed amount. Calculating the Magnification It is desirable to have a range of eyepieces of different focal lengths, to allow viewing over a range of magnifications. To calculate the magnification, or power, of a telescope, simply divide the focal length of the telescope by the focal length of the eyepiece (the number printed on the eyepiece): Telescope F. L. = Magnification For example, the AstroView 90 EQ, which has a focal length of 910mm, used in combination with the suppled 25mm Sirius Plössl eyepiece, yields a magnification of: 910 ÷ 25 = 36x Every telescope has a useful magnification limit of about 2x per millimenter of aperture. [. . . ] Before cleaning with fluid and tissue, blow any loose particles off the lens with a blower bulb or compressed air. Then apply some cleaning fluid to a tissue, never directly on the optics. Wipe the lens gently in a circular motion, then remove any excess fluid with a fresh lens tissue. Oily fingerprints and smudges may be removed using this method. [. . . ]