Bob's Knobs for Celestron 11" SCT We offer knobs for all versions of the Celestron 11” f/10 Schmidt-Cassegrain secondary with either standard or metric collimation screws, including Fastar, non-Fastar, and EdgeHD versions. Select knobs for your telescope from the list below. Special Note: The Celestron 11” SCT uses either standard 6-32 or metric M3 collimation screws. Allen, most silver Phillips, and set-style factory collimation screws have standard threads. Most black Phillips screws are metric. __________________________________ A. Knobs for C11 f/10 with Flat Secondary Housing and Standard Collimation Screw Threads Part: C11stdFits: Celestron 11” (28 cm) f/10 SCT versions (metal or carbon fiber tube) with flat secondary housing and standard collimation screw threads (not for CPC 1100 or EdgeHD). Does not fit the Starizona Hyperstar secondary (see Item C below).Knobs: Black plastic, 16 mm (5/8”) diameterThreads: Black anodized aluminum alloyNotes: Silver factory collimation screws usually have standard threads, but some silver Phillips screws have metric threads. Our hints will help you determine which screws are on your telescope. Make sure the knob threads match the factory screw threads before installing the knobs. The factory dust cover will fit normally with Bob’s Knobs installed. Celestron 11” SCTs manufactured prior to 2006 have standard collimation screw threads. __________________________________ B. Knobs for C11 f/10 with Flat Secondary Housing (non-Fastar) and Metric Collimation Screw Threads Part: C11metBO (black oxide steel); C11metSS (stainless steel)Fits: Celestron 11” (28 cm) f/10 SCT versions with flat secondary housing and metric collimation screw threads (most CPC 1100). Does not fit the Starizona Hyperstar secondary (see Item D below).Knobs: Black oxide steel (black) or stainless steel (silver), 12 mm (1/2”) diameterThreads: Black oxide or stainless steelNotes: Black Phillips factory collimation screws usually have metric threads, but some black Phillips screws have standard threads. Our hints will help you determine which screws are on your telescope. Make sure the knob threads match the factory screw threads before installing the knobs. Black oxide steel (shown in photo) 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. The factory dust cover will fit normally with Bob's Knobs installed. If your telescope has a factory-installed plastic cap over the collimation screws, it 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. (Black oxide steel) __________________________________ C. Knobs for C11 f/10 with “Trifid” Fastar Secondary Housing and Standard Collimation Screw Threads - (NOT EdgeHD) Part: C11stdfstFits: Celestron 11” (28 cm) f/10 SCT versions (metal or carbon fiber tube) with standard thread factory collimation screws and "Trifid" rotary cover Fastar secondary housing. Factory collimation screws are silver Phillips. These knobs will also fit the C11 with Starizona Hyperstar only if the collimation screws have standard threads.Knobs: Black plastic, 16 mm (5/8”) diameterThreads: Stainless steelNotes: These telescopes can have factory collimation screws with either standard or metric threads. Silver Phillips collimation screws are standard thread. Some black Phillips collimation screws are also standard thread. See our hints for more information. If you discover your knobs have the wrong threads, you can return them for a refund and order the correct knobs. Alternatively, you can order knobs with both standard and metric thread screws and return the unused set for a full refund. The factory dust cover will fit normally with Bob’s Knobs installed. The rotary secondary cover must remain open when the knobs are installed. The cover is cosmetic only and will not affect operation of the telescope. __________________________________ D. Knobs for C11 f/10 with Fastar Secondary Housing and Metric Collimation Screw Threads - (Edge HD) Part: C11metfstFits: Celestron 11” (28 cm) f/10 SCT versions (metal or carbon fiber tube) with metric thread factory collimation screws and Fastar secondary housing. This housing can have either a "Trifid" rotary cover or a simple knob in the center and no rotary cover. Factory collimation screws are black Phillips. These knobs will fit the C11 with EdgeHD optics. They will also fit the C11 with Starizona Hyperstar only if the collimation screws have metric threads.Knobs: Black plastic, 16 mm (5/8”) diameterThreads: Black oxide steelNotes: These telescopes can have factory collimation screws with either standard or metric threads. Most models with black Phillips collimation screws have metric threads. There are a few black Phillips screws with standard threads. See our hints for more information. If you discover your knobs have the wrong threads, you can return them for a refund and order the correct knobs. Alternatively, you can order knobs with both standard and metric thread screws and return the unused set for a full refund. Collimation screws on these telescopes are small with very fine threads. Knobs must be tightened gently (just enough to hold the secondary in place) to prevent damage to either the knob or secondary assembly. If your telescope has a rotary secondary cover, it must remain open when the knobs are installed. The cover is cosmetic only and will not affect operation of the telescope. SPECIAL NOTE: If your dust cover will not stay in place due to knob interference, contact us using the link below and we will send you knobs with a lower profile.
