Bob's Knobs Celestron C8 Standard Collimation Knobs

Bob's Knobs Celestron C8 Standard Collimation Knobs

  (2 Reviews)
✓ 2 year warranty


3x in stock shipped 1-2 working days

About this product

Model:  bk_c8_std
Part Number:  C8std

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 Post-1980 Secondary with Standard Collimation Screw Threads

Part: C8std
Fits: Celestron 8” (20 cm) f/10 post-1980 SCT with factory Allen or silver Phillips collimation screws, with or without Fastar secondary with silver collimation screws (C8 black, or gray; Ultima 2000; NexStar 8; others). This includes the post-2000 orange-tube. Will not fit pre-1980 orange tube or most scopes with black Phillips factory collimation screws.

Knobs: Black plastic, 13 mm (1/2”) diameter
Threads: Black Anodised Aluminium alloy


  1. These knobs will fit C8 models made prior to 2005 (except pre-1980 orange tube), and most post-2005 models with silver factory collimation screws.
  2. Most models with black Phillips factory collimation screws require C8 metric knobs (Item C below). However, 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. More information is in our Celestron technical paper.
  3. We provide spacers to raise the knobs slightly for easier use, but the spacers can be omitted if the knobs contact the inside of the full-aperture dust cover. Spacers are required for knobs installed on the Fastar secondary with silver collimation screws for proper clearance.
  4. 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.

Customer reviews

Average Rating (2 Reviews):  
Write a Review and share your opinions!

Rating (max 5):  
Definately worth fitting
15 September 2023  | 

Usual excellent delivery from flo.
Silly these are not fitted as standard.

Rating (max 5):  
Trepidation followed by joy
13 April 2021  | 

I was a bit apprehensive changing over my secondary screws with these as the collimation would need resetting. However after following the detailed instructions final collimation on a defocused star took about 60 seconds. I suspected my collimation was off before and yes it was. Itís bang on now and shall remain that way. Should have bought these ages ago!!


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