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Purchasing this set, containing both primary and secondary mirror knobs, eliminates the need to carry two different screwdriver types out into the field. It also saves you nearly 10% over the cost of buying the two sets of knobs separately. Installation of the knobs is a snap with the included instructions, and you can undo the modification at any time.

All the screws used in this Bob’s Knobs set are made of stainless steel. The knobs on the primary mirror collimating screws are five-point smooth fluted black plastic, 30 mm (1.25”) in diameter. The knobs on the primary mirror locking screws are knurled black plastic, 25mm (1”) in diameter. The difference in size and shape assures that you won’t confuse the function of the knobs in the dark. The telescope optical tube assembly will clear the rocker box with the collimation knobs installed.

The knobs on the secondary mirror screws are knurled black plastic, 13mm (1/2”) in diameter. These knobs are small enough not to impinge on the scope’s light path, yet large enough to grasp and turn easily, even when wearing gloves in cold weather. The factory dust cover will fit normally with the collimation knobs installed.

Bob’s Knobs recommends that you remove one primary mirror collimation screw at a time and replace it with a knob, then repeat the exchange one at a time with the remaining five screws. Check the thread size of each factory screw as you remove it and compare it to the replacement knob, as the collimation and locking screws use two different thread sizes. Repeat the procedure with the secondary mirror, removing one collimation screw at a time and replacing it with a knob, then repeating the exchange one at a time with the remaining two screws.