Bob's Knobs are the BEST option for tool-free collimation.
Simple to fit and easy to use.
Collimate your telescope without an Allen key or screwdriver!
Instructions are supplied but can also be found online as well as useful FAQ.
Images are representative and may not show the exact knob size / threads.
IMPORTANT: Please ensure the Bob's knobs threads and factory screw threads match before installation.
Knobs for C8 f/10 Secondary with Metric Collimation Screw Threads (not for EdgeHD or Hyperstar)
Part: C8metBO (black oxide steel); C8metSS (stainless steel)
Fits: Most Celestron 8” (20 cm) f/10 SCT made in 2005 and later with black Phillips factory collimation screws that have metric threads. Includes SkyWatcher SCT and non-EdgeHD Fastar.
Knobs: Black oxide steel (black) or stainless steel (silver), 12 mm (1/2”) diameter
Threads: Black oxide or stainless steel
- Most models with black Phillips factory collimation screws require metric knobs. A few post-2005 scopes have black Phillips collimation screws with standard threads. Here are some hints to help determine which screws your telescope has. Make sure the knob threads match the factory screw threads before installing the knobs; you may omit the white spacers if your factory screw threads are 10mm long. More information is in our Celestron technical paper.
- These knobs will fit the metric Fastar version only if it does not have EdgeHD optics. Scopes with EdgeHD optics require different knobs (Item D below).
- Black oxide steel (shown in photos) is for dry environments. Lightly oil the knobs periodically as an anti-corrosion measure. Stainless steel provides better corrosion protection in coastal or high humidity areas, or in places where dew or other condensation is common.
- The factory dust cover will fit normally with Bob's Knobs installed.
- Some telescope versions have a small plastic cover over the factory collimation screws. This cover must be removed and set aside when Bob's Knobs are installed. The cover is cosmetic only and will not affect operation of the scope.