The Tube Assemblies Arrived

The Tube Assemblies Arrived

I'm a bit disappointed with National Metal Fabricators. In spite of specifying 20.4" ID, +- .05", what I received for the lower tube assembly was 20" ID on one diameter, and 20.5" ID on another diameter. For this level of imprecision, I could have paid half the money and received the same or better results. I went with National Metal Fabricators at roughly twice the price of what Parallax quoted me, because Parallax warned that the tubes would be as much as 1/4" out of round--or considerably closer to round than what I have received.

I was able to, with a bit of squeezing and tapping, get the mirror cell into the tube. Part of why I built the flanges that hold the base plate in position with 2" of travel, was to be able to adjust the mirror cell fore and aft for the additional travel required for astrophotography. Something that has to be tapped into the tube isn't going to do the job.

I think the solution is going to be to find a woodworking clamp that lets me stretch the tube a little in the 20" ID dimension, and trim the base plate of the mirror cell by perhaps 1/8". Since I don't have a lathe big enough to turn something this large, I'm going to have to use a grinder instead--which isn't going to win any elegance awards.