Knobs for Newtonian 12” Primary

Bob's Knobs: Collimate your Schmidt-Cassegrain or Newton-Telescope without tools! It's easy! Just grab a Bob's Knob collimation thumbscrew and turn. You can even do it while looking through the eyepiece on most scopes. And you'll never drop that pesky little Allen wrench or screwdriver into the grass again. Installation is a snap with the included instructions, and you can undo the modification at any time.

These knobs will fit most Newtonian reflectors made by Guan Sheng Optical, including GSO, Hardin Optical, Meade Lightbridge, and Zhumell models. They have a screw diameter of 7 mm (collimation) and 6 mm (locking), and will usually fit your telescope if you select the knobs that match your scope’s aperture.

Primary collimation

• Knobs: Black plastic, 30 mm (1-1/4”) diameter, 5-point fluted
• Threads: Plated steel

Primary Lock

• Knobs: Black plastic, 25 mm (1”) diameter, knurled
• Threads: Stainless steel