Spider Support
Drill a 1/4" center hole through a block of hardwood 1/2" long and cut from the same square stick as was the wooden prism B. Saw it out to the shape shown in Fig. 61. For he vanes cut four rectangular pieces, 1½" x 2⅜", from sheet metal
not less than 0.012" thick, and attach them with small wood screws to the wood center piece.
Holes for attaching the spider to the tube must be drilled in the vanes so that they will be equidistant from the rotational axis of the diagonal and in a plane at right
angles to it. This can be done accurately on the lathe, or the special jig shown in Fig. 62 must be made to insure accurate location. Placed in this jig, with the center rod held rigidly between the two side boards, and the spider rotating in a fixed position, each vane will land in turn on the nail point shown. A light tap with a stick will impress this point in the vane.
After drilling out the holes thus marked, the vanes should be trimmed to a triangular shape. For holding the spider in the tube, short lengths of ¼" metal rod are used. Four pieces of this rod, about ⅞" long, are threaded for ⅝" of their length; a small hole is drilled through the unthreaded end, which is then slotted longitudinally with a hack saw for fastening to the vanes. (Rather than use rod, 1" long 14-20 round-head bolts can be bought and their heads sawed off.) Cotter pins may be used to attach these studs to the vanes. The holes in
For holding the spider in the tube, short lengths of ¼" metal rod are used. Four pieces of this rod, about ⅞" long, are threaded for ⅝" of their length; a small hole is drilled through the unthreaded end, which is then slotted longitudinally with a hack saw for fastening to the vanes. (Rather than use rod, 1" long 14-20 round-head bolts can be bought and their heads sawed off.) Cotter pins may be used to attach these studs to the vanes. The holes in the tube should be about 9/32" in diameter, all four located exactly in the same plane so that the spider will assume the position shown in Fig. 63, thereby giving access to the adjustment screw of the diagonal.
The inside of the telescope tube, adapter tube, vanes, and all other exposed parts should be thoroughly blackened.
Next- The Saddle
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