User manual ORION TELESCOPES & BINOCULARS MAKCASSCOLLIM

[. . . ] Star-Testing the Telescope Before you start adjusting the primary mirror of your telescope, make certain that it is actually out of collimation by performing a star test. Take your telescope out at dusk and let it acclimate to the outside temperature; this usually takes 30-60 minutes. When it is dark, point the telescope upwards at a bright star and accurately center it in the eyepiece's field of view. [. . . ] If circle is unsymmetrical, as in illustration on left, scope needs collimation. Alternatively, you can make a crude collimating tool out of an empty, black plastic 35mm film canister. It will not have crosshairs, so it won't be as precise, but it will be better than nothing. Cut 1/2" from the top lip of the canister and put a 1/16" to 1/8" diameter hole in the center of its bottom. Insert the film canister collimating tool into the focuser like an eyepiece with the bottom end out. IN 183 Rev A 03/02 Secondary mirror Front of telescope Reflection of your eye in secondary mirror Secondary mirror Front of telescope Reflection of your eye in secondary mirror Secondary reflection of inside of tube Reflection of inside of tube (misalignment) Figure 2a Figure 2b Figure 2a: If the telescope's optics are out of alignment the view through the rear opening of the telescope will resemble Figure 2a. Figure 2b: With the optics properly aligned the view through the rear opening of the telescope will resemble Figure 2b. Once you are ready to collimate, look into rear opening of the tube. If your telescope is out of collimation, it will resemble Figure 2a, a properly collimated scope will resemble Figure 2b. The direction of the misalignment in your telescope may differ from Figure 2a, but the diagram will give you the general idea of how things will look. Note there are six alignment screws on the back of the optical tube, three large and three small. You will need 3mm and 2mm Allen wrenches to turn these screws. These alignment screws push and pull the mirror cell in order to tilt it. When you loosen or tighten one of these screws, the other five screws must be adjusted as well to keep the proper amount of pressure on the back of the mirror cell. By making slight adjustments to how much the screws are tightened and loosened, you will change the alignment of the primary mirror. Look into the rear opening of the tube and locate the black crescent that shows the telescope is out of alignment. Note which way the front of the telescope would need to move in order to "fill" that black crescent and resemble Figure 2b. Then look at the back end of the telescope and locate the alignment screw that is in the direction that the front of the telescope needs to move. For example, if the view in your telescope resembled Figure 2a, then you would want to move the front opening of the telescope scope to the right. Then the alignment screw you would start with would be the screw on the right as shown in Figure 3. Your actions now depend on whether this alignment screw is a small or large screw. Please note that you will be working to adjust the mirror cell by keeping all the screws not too loose and not too tight. [. . . ] If your telescope appears collimated after star testing, it should not need adjustment again unless it is roughly handled. Turn the two small screws adjacent to the large screw (Figure 5d) clockwise no more than 1/4 turn. Repeat the above steps until the front opening is centered in the direction you wanted it to go. You may need to repeat this (or the large screw adjustment process) with other screws in order to align it in other directions. [. . . ]