Finally installed the famous Bob's Knobs mod. Specifically crafted for the Zhumell 12" model, these screws are almost perfect solution for a tool less collimation of the primary telescope mirror in the field. The transaction with these guys went smoothly. The delivery time was surprisingly quick.
Installation was done in place without the mirror cell removal necessary, one knob at a time. Just hold the springs in place.
Tension springs were replaced too, however not by their replicas from Bob's Knobs, which were unavailable from them at the time. I have them carefully crafted myself from some sort of a stainless steel spring, acquired from my local Ace hardware store.
Careful measurement, wise grips or hand grips, Dremel tool and most importantly - the safety glasses and leather gloves, because the hardened steel produces a lot of heat and sparks while grind, - all instruments I needed.
Installation was a snap too - the same one at a time mantra. But have your forward screws in all the way to relax the original springs for easy removal.
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