These knobs make it easy to collimate your Meade 8” f/10 Schmidt-Cassegrain 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. While it is a long reach, you can probably still adjust the collimation yourself 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 8” f/10 Meade Schmidt-Cassegrain telescopes, such as the 2080, LX10, LX5, LX6, Premier, LX50, LX100, LX200, etc. Some of these scopes were also available in a faster focal ratio f/6.3 version. These particular knobs work only with the f/10 versions of these scopes, and are not for the f/6.3 models. The f/6.3 scopes need knob set #BKM863.
Important note: These knobs work only with current Meade scopes that have three collimation screws in their secondary holder. Meade has re-designed the secondary mirror assembly on their 8” SCT with six screws instead of three screws that appear on the older design. The three outer screws hold the secondary housing parts together, and the three inner screws are for collimation. Knobs for the six-screw secondary must not be used on scopes with the three-screw secondary holder! The screws are too long and they can contact the back of the secondary mirror. The correct part number for knobs for the 6-screw Meade secondary version is #BKM810S.
The Bob’s Knobs collimating screws themselves are made of black anodized aluminum alloy. Their knobs are black plastic, 13 mm (1/2”) in diameter. Some early Meade 2080 telescopes have only two collimation screws. Knobs are available on a special order basis to fit this scope.
Since the factory dust cover contacts the secondary housing when you put it on the scope for storage, additional clearance is needed to make room for the knobs. The knobs come with a set of spacers that attach to the inside of the dust cover to move it slightly away from the secondary assembly so the dust cover will clear the knobs. You can also press the center of the lightweight aluminum cover outward from the inside with your thumbs to contour it for additional clearance. (For the LX90, the factory dust cover will fit normally with Bob's Knobs installed without any spacers or contouring.)
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.