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The tube pictured is an old RCA 931a I got "new" in the box, manufactured in April, 1945 according to same. Well, unless air has leaked into it, it should be fine, there's not much to go wrong with one of these.
Construction was simple, sort of. First tubing of the right sizes was obtained from McMaster-Carr. Then the larger piece that contains the tube was put into the mill and a slot cut in it where the light is to enter. The other piece was then notched with a bimetal hole saw. This part was WAY too exciting, and almost broke the drillpress. It's just not rigid enough to keep the teeth of the hole saw pulling themselves into the metal too fast, and won't go slow enough. So all this was moved to the milling machine at 60 rpm, and there it went fine. The pieces were clamped in a vise and wire welded.
Next, end caps were needed. I could have just cut some sheet metal and welded it on there, I suppose, but I wanted something a bit more elegant, and removable. So, a jig was made by using a 1-5/8" Forstner bit to drill about halfway through a piece of very hard oak from some 100 year old flooring. This became the die. For the punch I just used another piece of the 1-1/2" inch tubing with the edges rounded a bit. Plugging in a 2" copper flashing washer and pushing in the pipe with a press made the caps. The top cap was then soldered in place with the normal plumbing stuff, and all tested for light tightness.
For the base, I punched a hole in one of the copper caps to hold an octal tube base. This is held in with a snap ring, then J&B weld for light tightness. The piece of PVC pipe in the picture is an insulating spacer to keep the resistor chain from shorting to the pipe, and to keep the tube more or less in place. Not shown is a piece of cardboard I intend to add as a shim to make the tube a friction fit.
Of course, to be cool, anything telescope related must be black, so I painted it all with flat black spray paint. Unfortunately, the 1.25" tubing is that, exactly, and so are the eyepiece holes in the scope gear, so that paint and some metal had to go to make things fit.