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Accessories - Bob's Knobs Collimation Knobs For Celestron 8" SCT F/10 - Metric
Accessories - Bob's Knobs Collimation Knobs For Celestron 8" SCT F/10 - Metric

Bob's Knobs Collimation Knobs for Celestron 8" SCT f/10 - Metric

Bob's Knobs
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Estimated Arrival: Between Dec 07 and Dec 13. *ETA to USA Only

Shipping & Returns: Satisfaction guaranteed 30 day return policy.


Bob's Knobs offer knobs for all versions of the Celestron 8” f/10 Schmidt-Cassegrain secondary with either standard or metric collimation screws, including Fastar, non-Fastar, and the classic orange tube. Select knobs for your telescope from the list below. Please use care to select the correct knobs for your telescope. Each knob set is different and they are not interchangeable. Price is for a complete set of knobs.

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. Will NOT fit Celestron telescopes made before 2005.


  1. 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.
  2. Some C8 scopes have metric collimation screws that are 10mm long rather than the more common 8mm, and you should install knobs without the white spacers.
  3. 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).
  4. Black oxide steel (shown in photos) is for dry environments. Lightly oil the knob top and knob serrations 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.
  5. The factory dust cover will fit normally with Bob's Knobs installed.
  6. 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.
  7. The Celestron 8” SCT uses either standard 6-32 or metric M3 collimation screws. Allensilver Phillips, and set-style factory collimation screws have standard threads. Most black Phillips screws are metric. See our hints and our Celestron technical paper.for more information. If you order knobs with the wrong screws, contact us using the link at the bottom of this page for return instructions.



Black plastic, 13mm (1/2”) diameter


Black anodized aluminum alloy



We know that once you've placed your order, you are anxious to receive it! We make every effort to get your order shipped out to you as quickly as possible.

As soon as you place your order, you will receive an order confirmation e-mail. This means that we have received your order in our system and pre-authorized your credit card for the purchase. We will process the charges to your credit card and your order will ship within five business days from the date of your order. We will send you tracking information within 24 hours of your order leaving the warehouse to the e-mail address you provided when checking out.  If you do not receive tracking information from us within six business days of your order, feel free to follow up with us at

Standard shipping time in the US is between 3-5 business days, though it can vary slightly depending on the destination. We typically For updates on your shipment you can enter your tracking number here.

We distribute nationwide via UPS and Fedex. Unfortunately, at this time we are not able to provide expedited or international shipping.