Lots of shiny sawdust. . .

Feb 8. I marked the 1-1/2 x 3/8 metal stock and cut it to length. I cut each 48-inch bar into two equal lengths, then divided each of those. Then I lined up the 4 pieces and cut them to uniform length, as close to 12-inches as errors and kerfs would allow. I marked the pieces of each set to prevent unfortunate mixups. It's far more important that the 4 pieces in each set be equal in length than that they be exactly 12 inches long.

I lined up the first four pieces and set the corrector on top of them for a plausibility check. Dimensions look fine.

Then I cut two identical beams from a 1-1/4 x 1/2 inch bar.

I trimmed off a short length of 2-inch I.D. tubing to accomodate the focusser (and, eventually, most likely a Baader MPCC). This piece is a placeholder until I know the length required to bring sensors to focus.

And then I cut 7/8-inch stock into 3-inch lengths. I cut 24 blanks but will likely only need 20 need 28 for this project (I should read my own notes). One end will be turned to slip fit inside the truss tubes and the other will be milled and drilled to mate to cages made from the flat bars.

Total time from "Where are my goggles?" to "Here's the kit" was about an hour. Beats hacksawing by huge margins in both time and quality.

In the afternoon, I assembled one of the 3 square frames required (one for the mirror cell, one for the corrector cell, one to connect the top and bottom trusses). I made this one from the 12-inch bars marked "1" in the picture at right. I don't know which frame this will be when all is finished.

Drilling, tapping and connecting it up was as confusing as one might expect. I ended up with two superfluous holes. Bolted together, the frame seems surprisingly solid. "Surprising" because it was like wet spaghetti until I cinched down the fourth and final screw, and then the frame became tolerably rigid. It's always like that with trusses and distributed forces, isn't it? Isn't it? Tell me it is.

Feb 9. The first box worked out but seemed a lot of trouble. The next went together more smoothly (nevermind the recipe, nothing brilliant), and the third would have been easiest except I finally snapped a tap in one of the blind holes (I say "finally" because I do this with regularity when I get impatient and apply force out of line and unsteadily).

I need to find a good cutting fluid. WD-40 isn't. Aluminum gummed up the drills and the tap and resisted effective cleaning. I drilled the last three holes with an oversized bit which meant the tap cut shallower threads (effortlessly). They still feel solid and have plenty of grip. There are alternatives. It's a telescope, not an airplane.

From the tube stock, I cut 8, 12-inch truss tubes and 6, 18-inch tubes. I suppose it was beneficial to waste years of my life with a hacksaw, but that metal-cutting blade for the miter saw is the ticket. I cleaned up the north end of the basement and turned next to the south end, where the machine tools live.

Next: turn the truss tube adapters . . .

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Text & Photos by David Cortner
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