I’ve managed to work some more on my Telescope. One of the things that is very important in a telescope is that it be balanced. The last thing you want to happen is to point it at some pretty double star and say to your friend, “Take a look!” and have the scope move eight inches toward the ground.
The center of balance determines the size of the trunnion bearings. So until I know where it balances, I can’t know the size of them. Before I determin the balance, all the parts of the telescope must be assembled. Up to this point I have been running into technical difficulties.
Mathmatically I calculated where the balance point should be, but when I did some rough measurements, it was beginning to look like they were way off. I decided to simulate the balance with a mock-up of something similar to what I would eventually do.
And today, with the completion of the final part, I can report that the balance of the telescope is very close to what I predicted it would be.
The last part I had to make was a baffle to keep stray light from street lamps and houses out of my field of vision. The baffle needed to be very light weight so that I wouldn’t have to add extra weight on the other side of the pivot point to balance it out. I chose to use a polystyrene “for sale” sign. It was cheap, came in 18” x 24” size and is easily molded on a vacuum mold over a form. The form is a saddle shape that I placed on top of a vacuum box (it’s similar to a down draft table, and in fact, that is what I will use it for from here on out). My shop vac attached to a hole in the sides sucks the hot plastic For Sale sign over the top of the mould, and presto-change-o I have the shape I need. Cut it with a utility knife, paint it black so it doesn’t reflect light, and I have a light baffle.
Here is a picture of my telescope right before adding the baffle to it. The scope is resting on a temporary U shaped fork. it balances on those two 3/8” bolts you see. The pipe is an aluminum tube. The main mirror fits in the large 12” dia opening.
At the rate I am going, I should be done with this thing in February sometime… Then I can finally make my workbench :) Its going to be a “jack-bench”.
Edited on 11/15 to include these four pictures of the top end as well as the main mirror installed. The main mirror is not silvered yet because I am still adjusting it’s paraboloidal shape.
As it turns out my calculations for the balance point were right on… Physics matches reality and that’s a good thing. :)
-- Telescope Maker, Woodworker, Brewer, Gizmologist, Gardner, Lawn Mower