30.06.2020 PH-20 Preventing telescope rotation on the camera plate.

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One, major problem I have found so far is the telescope [and attached camera] rotating around the fixing screw on the camera plate. I have tightened the [drop ring] thumbscrew as hard as finger tight will allow. Still the telescope objective springs half an inch from side to side. The camera even further due to the much greater "leverage."

The Kowa telescope foot and narrow ring may have some flexibility. Though I think the movement is mostly around the fixing screw. Probably due to the flexing of the rubber pads on the Sirui camera plate.

I am using the longer PH-180 plate for maximum freedom to slide the plate through the head for system balance. Ideally I need some means of restricting plate rotation. A small hole and a slot are provided in the Kowa's foot. Though the large diameter of the thumbscrew means these holes are largely inaccessible. The very shortness of the Kowa foot is another negative factor.

Manfrotto do an anti-twist clamping plate based on an L-shaped casting. The downside is the very small size relative to the very long mechanical system of telescope and camera. I can't just start drilling holes in the impeccable Kowa telescope body to fix something to the tube. So any restraint has to be fixed to the camera plate.

A curved 'crutch' to stop the tail end of the telescope body from moving sideways might work. The problem then is the stay-on bag getting in the way. A taller crutch could locate on the tubular body section at the tail end of the telescope. A right angle profile, in aluminium, is bolted to the rear end of the camera plate. Then a vertical crutch [plate with half round cut-out] is bolted to the angle piece.

Since this restraining 'prop' is fixed to the plate it will slide with the plate during balancing operations. A plastic plate would pass unnoticed in this position. I don't want to use aluminium for the upright plate. It would permanently mark the Kowa body black over time.

An hour later I had a prototype and it worked amazingly well! From half an inch of rubbery wobble, from side to side, to barely detectable movement.

Just a short length of scrap aluminium angle and an off-cut of kitchen cutting board. It needed a bit of inward bias on the angle to pull the crutch tightly into the tail end of the telescope. I have heavier sections of angle profile to make a much smarter and beefier job. That can come later if it proves to be worthwhile. There may be a flaw in the design somewhere which I haven't discovered yet.

I was delighted to see that I had colour matched the grey plastic to the Kowa "uniform." Quite by accident. It was that, or bright red! The scruffy bit of thin angle is hideous and must go!

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