Psalms 19: 1 "The heavens declare the glory of God...
The heavens are glorious! There is almost nothing as beautiful in the universe as a dark clear night and the sky full of millions of stars. I have always been interested in telescopes and their power to let us see deeper and clearer into the heavens. My first telescope was a used low quality 4" refractor with an equatorial mount and cheap eyepieces. That thing helped me to understand how telescopes work, and the function of the mounting system, but it didn't last long before I wanted something that would allow me to see more.
After a lot of researching, I decided to buy a fairly good mirror set and build an experimental telescope from junk parts and see if it worked. If that worked, then I would put a little more time into building a better unit.
I will add details of both versions of telescope.
HERE is a great video from John Dobson explaining how the reflector telescope works and how to make one for low cost. John Dobson had some very odd views about many things (including religion), but is a patient and kind teacher of astronomy and telescope construction.
HERE is the final version of my 8" Dobsonian Telescope (with the cover on the mirror box). It is f-8, so pretty long focal length and only tall people can use it when looking at the zenith (or short people on a ladder!). The plywood for the base was from my wrecked service truck box. The aluminum for the focuser mount was from trim from an old camper, and the light shield was the shell of an old water softener. The mirror cell was a aluminium from a broken ladder that I cast using a waste oil furnace I made a while ago. Why I use junk to build stuff is because I don't have much money and so if you are going to have things, you have to make them. This telescope worked pretty well on the traditional dobsonan base, but it was going to stop working in the winter, so I modified it so it could be left outside in the rain and snow. I welded an alternate azmuth mount using steel recovered from my old service truck and some used front bearings from an even older truck. I did have to buy the main aluminum 2" tube, but it was only $2 from the scrap yard!
13.5" Dobsonian Project
An 8" telescope is useful for many observations, but in order to see actual detail in globular clusters or planetary nebula you have to have a larger aperture.
The next project was to make a larger telescope, but again, I don't have $1000 (or more) for a mirror, so I am trying to cast a mirror blank from used glass and then grind the primary mirror. I tried several versions of plaster to make a small kiln, but the plaster kept cracking once it got to +1000'F no matter what recipe I tried, so now I am using a friends electric ceramics kiln and the largest it will cast is 13.5" diameter.
I was given a fairly large double pane window with tempered glass. I cleaned both sides with windex, then acetone. Then laid the window down on a plastic sheet and covered it with another sheet. Then I broke the top pane with a small hammer. Since it is tempered, it broke into a million small pieces but stayed together. I then scooped the glass into a clean pail and did the same for the next pane. Altogether the window yielded 80 lbs of nice uniform 1/4" frit lime soda glass.
HERE I made a fixed post mirror polisher from an old bicycle. I will try to use this to grind the glass once I get the blank done.
Fall 2015 First try casting glass mirror blank- My friend made a clay flat bottomed dish about 12" diameter that I used as a mold. I used cut pieces of old plate glass and it worked OK. 1700'F for 3 hours melted the glass but it still had bubbles on its surface. The mold cracked a bit so I had to improve the system.
March 2016 I had a fellow at the machine shop next to where I work bend me a piece of regular sheet steel into a 14" ring. It would save a lot of grinding if I could cast the rough mirror curvature into the glass, so I made a gypsum disk the same size as the mirror I wanted to cast. Then used a scraper and sand paper to make the rough mirror curvature in the positive mold. This gypsum mold was to be used to press casting sand to the shape of the mold negative. Kiln paper was used to line the metal ring and the casting sand. The first test run the little glass pieces melted right down and there was only very tiny bubbles present in the glass.
The mold was readied again for another try, but better attention to filling in near the edge of the mirror. This try will be run at 1550'F for the five hours and if that works, then a second layer of frit will be added and fused at a lower temperature to prevent the glass from running. This should make a very light weight mirror blank that will be very rigid.
12" LX-200 I found this telescope optical tube on a buy and sell website. It works pretty well but was very dirty. I cleaned the corrector plate recently and will attempt the mirror when I have time. My 13.5" dob project has a lot of technicalities to work out so when I found this telescope for a fairly low price, I bought it. The first thing I had to do was to design the mount system. I like the German Equilateral type but I figured if I was making it from scratch, I might as well balance the thing so I wouldn't need any counter-weights.
HERE and HERE and HERE are some pictures of that project. The last one shows the corrector plate before cleaning.
Reiner Vogel's website has a lot of useful info
Stellafane is an amateur telescope making website. This is really good stuff.HERE
Jay Freeman's page is one of the most understandable and encouraging web info sites I have found.
Old.Observers.org useful observing guide to find stuff
R.F. Royce is a good mirror maker who has the best info on cleaning the optics I have found.
HERE is an encouraging website for DSO observing.