Thursday, September 29, 2011

Primary's alignment mod

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.

The factory made spring were cut to the size of originals. The resulting 3-coil pieces' ends were grind far enough to provide the maximal surface of contact, which is perpendicular to the spring's main axis (see the picture).

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.

Sure thing I've lost in the travel distance somewhat because this new spring is beefier, but now it is definitely holding the weight of the mirror cell during collimation of the telescope. Fortunately it's long enough for any practical application nevertheless. In fact, opposite tension knobs are all that necessary for the final fine tuning of the collimation using the Airy Disk (Star Test) method. But those images are for my next post about the actual collimation challenges.

Very convenient, indeed.

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