The manufacturer Bob's Knobs supplies various collimation screws for Schmidt-Cassegrain, Ritchey-Chrétien and Newton telescopes.
The selection includes screws for primary and secondary mirrors for optics between 5" and 16". In addition, Bob's Knobs offers mounting screws for various mounts from Celestron (CGE, CGE Pro, NexStar), Losmandy (GM-8, G-11) and TeleVue (Gibraltar).
Please refer to the respective specifications and technical data to find the right screws for your model!
Fits: Pre-1980 Celestron 8” (20 cm) f/10 SCT with orange optical tube and factory set-style collimation screws. These screws can be either Allen or slotted.
- Knobs: Black plastic, 13 mm (1/2”) diameter
- Threads: Black anodized aluminum alloy
Notes:These knobs will fit orange tube C8 models made prior to 1980. The secondary has factory set-style collimation screws with a fourth central screw in the secondary housing.
Two sets of knobs, each with a different screw length, are included with your order. Use the length that fits your telescope best. There should be two or three screw thread turns above the secondary housing and the dust cover should fit without contacting the knobs.
Do not adjust the center screw; this is the secondary pivot screw.
