| These knobs make it easy to collimate your vintage 2006 and later Celestron C5 for optimum image quality. You don’t need any tools, so you never have to worry about losing a tiny Allen wrench or screwdriver in the grass in the dark. You adjust the collimation while looking through the eyepiece, so there’s instant feedback about how your optics are performing. Installation of the knobs is a snap with the included instructions, and you can undo the modification at any time. This knob set works with all 5" Celestron Schmidt-Cassegrain telescopes made in 2006 and later (such as the NexStar 5SE) that use black Phillips-head collimating screws as shown in the feature image below. They do not work with Celestron C5 scopes made prior to 2006 or all post-2006 C5 scopes that use silver collimation screws. Scopes using the silver collimating screws require the #BKC5 standard knob set. Check that the screw threads on the knob set you buy matches the factory collimating screw threads before installing. The collimating screws in this knob set are made of black-oxide steel. Their knobs are also black-oxide steel, 12 mm (1/2") in diameter. Some versions of the C5 have a small snap-in plastic cover over the factory collimation screws. This cover must be removed and set aside when these collimation knobs are installed. The cover is cosmetic only and will not affect the operation of the scope. The factory dust cover will fit on the scope with Bob's Knobs installed. The three collimation screws hold the secondary mirror and its mounting plate to the secondary housing. The mirror mounting plate pivots on a tang or spring at its center, and the collimation screws, which are threaded into the plate, adjust the mirror tilt (or collimation). Do not remove more than one of the original collimation screws at a time when installing Bob's Knobs, as the secondary mirror might fall off (if all three screws are removed at the same time), or the secondary can pivot inside the tube, scratching the corrector plate (if two screws are removed simultaneously). By removing only one factory collimation screw at a time, replacing it with a knob, and repeating this process for the other two collimation screws, there's no danger of dropping the secondary mirror. The instructions also recommend pointing the optical tube assembly slightly downward during the installation of the knobs for an added safety measure.
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