Thursday, November 14, 2019

Baby Telescope

I moved the primary mirror .5" closer to the diagonal and it is now a decently functioning telescope.  Most of the work on this rebuild was making sure that I could collimate it.  (The previous diagonal holder was a stalk that was held in the eyepiece focuser by a screw.  There was no practical way to adjust the diagonal's position relative to the primary mirror.)  I was able to collimate it to a level that it has never seen before!  I will need the primary and diagonal recoated.  From using it this evening on Bogus Basin, I have some confidence that it will make a fine scope for the Moon, the Orion Nebula, and other low magnification objects.  (I never had any delusions that my first mirror was great.)

How to mount it is the next issue.  I had originally put a 1/4"-20 hole in the bottom of the tube, but this is unsatisfactory.  The first time I mounted it on a camera tripod, it barely attached at first.  I did this 25 years ago.  Now I know that you should chamfer threaded holes.  So I did so, and perhaps too aggressively; this is not a very thick PVC tube.  It seemed to thread on, then rolled off into my fortunately present hands.  I have some 4 5/8" ID rings which I will turn into 4.5" rings with a layer of foam rubber.  These rings have 1/4"-20 holes in the bases.  I just need to make an assembly on which to mount these rings.

This will have to wait.  My mill is at Sherline getting fitted with limit switches, and trying to figure out why Axis X on the controller keeps blowing its fuse.

I turned on the TV and put the baby telescope (telescopette?) on the table.  Even at 50x (a 7mm eyepiece) it was nicely sharp.  Maybe I did a better job on this mirror than I realized.

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