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Airline portable design questions: 18"

Started by williamichang, 07/16/2003 11:57PM
Posted 07/16/2003 11:57PM Opening Post
My concept of a "dream scope" is an 18" whose sides are truncated to fit 14x18 (!). I have tried to observe the effects of such an aperture mask (two sheets of paper) -- basically undetectable to me until the blockage is great. Additionally, some contrast should be reclaimed by using a smaller diagonal, since the light-path past it is 2" shorter. The 13.5x18 mirror will have 90% of the light-gathering power of the full 18", but is mechanically only 14" wide, another advantage.

I imagine four long (2-section?) poles arranged in "anti-parallel" fashion: looking from the side, the poles converge from 18" apart to around 9"; looking from the top/bottom, the poles diverge from 14" to 16". The (4) trapezoidal facets help make the truss structure more rigid, and also miss the light cone. The poles on each side are joined by boards (one holds the focuser); a pair of curved vanes, joined at the center, connect across the poles and also hold the secondary cell/mirror. (I don't know if a full secondary cage is necessary for structural/vibration reasons.) The poles may be too long to transport unless they are telescoping or sectional.

Anyway, although this is currently just a "concept", I think I would be willing to commission an 18" thin-mirror/cell with truncated sides... any takers? :-)

I realize the above descriptions are hard to get across without pictures. In any case questions, suggestions, or critiques will all be greatly appreciated!

-- William Chang (Saratoga, CA)

p.s. does anyone have a badly chipped 18" thin mirror? ;-)