Bob's Knobs offers knobs for the Astro-Tech, GSO, iOptron Photron, MallinCam VRC, Orion (US), and TPO OS 6”, 8”, 10”, 12”, and 16" Ritchey-Crétien secondary. Select knobs for your telescope from the list below. Price is for a complete set of knobs.

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

Part: AT6RC

Fits: Astro-Tech, GSO, iOptron, MallinCam, Orion (US), and TPO 6" f/9 RCT secondary (solid or truss-tube)

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.

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

Part: AT8RC

Fits: Astro-Tech, GSO, iOptron, MallinCam, Orion (US), and TPO 8" f/8 RCT secondary (solid or truss-tube)

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.