[ATM] 16" mirror

["Alan K. Henderson" <alankh@ev1.net>]

Actually, the mirror is 16.5" - it has a quarter-inch L-shaped bevel around the edge (which allows the use of clamps that won't block the reflective surface). It is 3.5" thick and weighs 50 pounds. I plan on a 6-point cell. The cell (including support bars) will be constructed from tubular steel; the tubular aluminum I see at Home Depot looks too wimpy for the job. It will be an inverted T, with two lengths of tubular steel extending from the crossbar to the edge ending in the lower supports (which will be 50 degrees apart). I may use L-cross-section steel extrusion for the crossbar to reduce cell weight slightly.

1. I'm not too worried about the dimensions of the lower edge support bolts; if I have to (and I probably will), I can easily fashion a brace underneath each one. But the collimation bolts have to be able to support the weight of both mirror and cell without bending when the scope is pointed toward the horizon. How thick should the collimation bolts be?

2. The three support bars have to collectively support 50 pounds without bending. Plop calculates support bar length (well, the distance between the points) at 4.629 inches. Will 1" tubular steel be sturdy enough for the job?

3. Mirror cooling is going to be a serious issue with such a thick mirror. Will extra cooling fans help? Any other cooling ideas?

Alan
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