ASTRO-TECH (GSO/Orion/TPO) RCT Series

We offer knobs for the Astro-Tech, GSO, Orion (US), and TPO 6”, 8”, 10”, 12”, and 16" Ritchey-Crétien secondary. Select knobs for your telescope from the list below.

A. Knobs for Astro-Tech (GSO/Orion/TPO) 6" f/9 Ritchey-Crétien Secondary

Part: AT6RC
Fits: Astro-Tech, GPO, Orion (US), and TPO 6" f/9 RCT secondary

Knobs: Black plastic, 16 mm (5/8”) diameter
Threads: Stainless steel

Notes:
  1. If the dust cover cannot be installed because of knob height, you can use a shower cap in its place.

$25.95

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B. Knobs for Astro-Tech (GSO/Orion/TPO) 8" f/8 Ritchey-Crétien Secondary

Part: AT8RC
Fits: Astro-Tech, GPO, Orion (US), and TPO 8" f/8 RCT secondary

Knobs: Black plastic, 16 mm (5/8”) diameter
Threads: Stainless steel

Notes:
  1. 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 one or two screw thread turns above the secondary housing. In most cases the dust cover will fit without contacting the knobs.
  2. If the dust cover cannot be installed because of knob height, you can use a shower cap in its place.

$25.95

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C. Knobs for Astro-Tech (GSO/Orion/TPO) 10" f/8 Ritchey-Crétien Secondary

Part: AT10RC
Fits: Astro-Tech, GSO, Orion (US), and TPO 10" f/8 RCT secondary

Knobs: Black plastic, 16 mm (5/8”) diameter
Threads: Stainless steel

Notes:
  1. The factory dust cover may contact the knobs when installed, but the cover will remain in place. If desired, a shower cap can be used as a substitute cover.

$25.95

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D. Knobs for Astro-Tech (GSO/Orion/TPO) 12" f/8 Ritchey-Crétien Secondary

Part: AT12RC
Fits: Astro-Tech, GSO, Orion (US), and TPO 12" f/8 RCT secondary

Knobs: Black plastic, 16 mm (5/8”) diameter
Threads: Stainless steel

Notes:
  1. The factory dust cover will fit normally with Bob’s Knobs installed.

$25.95

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E. Knobs for Astro-Tech (GSO/Orion/TPO) 16" f/8 Ritchey-Crétien Truss-Tube Secondary
AT16RC

Part: AT16RC
Fits: Astro-Tech, GSO, Orion (US), and TPO 16" f/8 RCT truss-tube secondary

Knobs: Black plastic, 16 mm (5/8”) diameter
Threads: Stainless steel

$25.95