I just picked up a used ES 152 "Comet Hunter" Mak-Newt and am trying to get it collimated. I used a sight tube to adjust the secondary, and believe I've got that taken care of, but I'm having trouble with the primary.
I'm using a laser collimator and have loosened the locking screws in the center of the three thumb screws with a hex key. No matter how I tighten or loosen the three thumb screws, the laser dot doesn't move at all. If I press down on one of the loosened thumb screws, the mirror moves (and the laser spot moves), but no amount of fiddling with the screws can get it to hold that position.
I tried removing the mirror cell from the OTA, and I don't see anything obviously wrong. There are springs between the mirror cell and the thumb screws, so I'm assuming tightening the screws is meant to pull the cell. I'm wondering if there's an opposing push spring that's missing? Or maybe there's some trick to doing this? On my dob, I just rotate the thumb screws and the mirror moves!