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Airline portable design questions: 11"

Started by williamichang, 07/16/2003 11:50PM
Posted 07/16/2003 11:50PM Opening Post
I have been designing several airline portable scopes, what I call the "91422 Series" (9x14x22 carry-on size). Disclaimer: I have not built a scope before :-)

I now have virtually all the parts for an 11" f/4.5 modelled after the StarMaster ELT (using original 12.5" ELT poles and connectors), but more compact. The mirror box (to be built) is 16Lx14Wx9H; secondary cage is 14Dx7.5H; removable alt-bearings are 14"D semi-circles; the 7"H rocker sides are hinged on the inside and fold down for transport; when upright the rocker sides press against the edges of the rocker base through tensioners.

A major challenge is the needed low-profile mirror cell -- every inch counts since a taller cell means less room inside the mirror box to nest the UTA (which partially encloses the primary); the UTA in turn has to be taller for the extra light-path, since the poles are fixed at 34"L. What if I "hung" a square mirror board at three or four points along its perimeter, using bolts/springs/wingnuts (or push-pulls) in reverse fashion, i.e. wingnuts on top? Am I more likely to run into rigidity/play issues compared to the usual design, wingnuts on the bottom and closer together? Has anyone tried a low-profile cell like this? (I realize the gap between the mirror board and rocker is "dead space" normally taken up by the cell and protruding collimation bolts; however, those things can't stick out of a portable, fixed-height mirror box.)

Finally, should I use a sling for the 11" 1.5"-thick mirror, or just silicone in-between the mirror perimeter and angle brackets (like describe in S&T last year)? Any other suggestions for the cell, commercial or otherwise?

Any questions, suggestions, or critiques welcome and appreciated.

-- William Chang (Saratoga CA)

Posted 07/17/2003 03:28PM #1
William,

you mentioned the StarMaster 11 ELT. There was some discussion lately on SM group that some time ago, Rick considered to produce airline portable 11" Starmaster but put the idea aside due to lack of interest. Several people in the discussion revealed interest in such scope. Maybe Rick needs a public "push" to move in this direction.

To answer your question re: low profile mirror cell, have alook here;

http://www201.pair.com/resource/astro.html/regular/products/cpt/cell.html

David