User manual ORION TELESCOPES & BINOCULARS SKYQUEST AD

[. . . ] NOTE: If your SkyQuest XT8 has six evenly spaced screws on the back end of the optical tube (bottom of the primary mirror cell), then this addendum applies to your telescope. If your SkyQuest XT8 has three sets of two screws on the back end, then this addendum does not apply, and the provided instruction manual is complete. Addendum to the Instructions: Primary Mirror Adjustment #9980 SkyQuest XT8 Dobsonian Reflector Telescope There has been an improvement to your SkyQuest XT8 that is not mentioned in the provided instruction manual. [. . . ] The tilt of the primary mirror is adjusted with the three springloaded collimation screws on the back end of the optical tube (bottom of the primary mirror cell); these are the screws with the springs visible just under the mirror cell casting (Figure 18). The other three screws lock the primary mirror's position in place; these screws must be loosened before any collimation adjustments can be made to the primary mirror. To start, unthread the screws that lock the primary mirror in place a few turns each with a Phillips-head screwdriver (Figure 19). Now, try tightening or loosening one of the spring-loaded collimation screws one turn (Figure 20). Look into the focuser and see if the secondary mirror reflection has moved closer to the center of the primary mirror reflection. Repeat this process on the other two collimation screws, if necessary. It will take a little trial and error to get a feel for how to tilt the mirror in this way to center the reflection. (It helps to have two people for primary mirror collimation, one to look in the focuser while the other adjusts the collimation screws. ) Do not loosen (i. e. , rotate counter-clockwise) each collimation screw too much, or the screw will completely unthread from the mirror cell casting. Rather, try tightening the other two collimation screws. Once the secondary mirror reflection is centered in the primary mirror reflection, retighten the screws that lock the primary mirror's position in place. [. . . ] The tilt of the primary mirror is adjusted by turning one or more of the three spring-loaded collimation screws. 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 139 Rev. [. . . ]