TELESCOPE
MAKING
20.1 inch pyrex mirror blank
| AMATEUR TELESCOPE MAKING |
20.1 inch pyrex mirror blank |
Amateur telescope making - often called "ATM" - is both an art and a science. A variety of skills are required to complete a self-built
instrument. It's not unusual for a telescope builder to find
themselves involved in woodworking, metalworking (machining), and optical fabrication.
The most common type of telescopes built by amateurs is the
newtonian reflector. It uses a primary mirror whose surface must be
polished to an accuracy of only a few millionths of an inch.
Amazingly, no expensive or high tech equipment is needed to attain this level of surface accuracy.
My first venture into telescope making was a dobsonian mounted newtonian reflector. The aperture of the scope is 6 inches and it has a focal length of about 48 inches - which yields a focal ratio of F8. This is a very common size for a beginners telescope. It provides excellent perfromance on planets, and is very portable. It also does a good job on star clusters and brighter nebulae.
The mount is constructed of 3/4 inch plywood, and the main tube is a common concrete form tube (cardboard) commonly called "sonotube". The entire scope was sealed with primer-sealer and then painted with battle-ship gray floor enamel in order to make it waterproof.
The mirror, being my first attempt at optical work, took a total of about 25 hours to complete. The total construction costs (not including the purchase of eyepieces) was about $250. This wasn't much of a savings over the cost of a commerically made 6 inch dobsonian, but having done it myself, it was a lot more rewarding.
The little 6 inch scope doesn't get as much use these days, since my telescope collection has begun to grow. I still drag it out on occasion. I doubt that I'll ever sell it - it has to much sentimental value.
No sooner than the 6 inch scope was finished, I was already planning a larger scope. Aperture fever had struck, as it does about 90% of all amateur astronomers, and about 99% of all amateur telescope makers.
The next instrument was to be a 12.5 inch truss-tube scope. It was motorized and had a compter tracking system. It turned out great, but had one major shortcoming - it wasn't an instrument that you wanted to drag out and setup for quick observing sessions. It took at least 30 minutes to set-up.
The next project was again taking shape shortly after the previous one had been finished. I wanted the aperture of a 12.5 inch scope in a package that was easy to transport and quick to setup. This led to a two-section dobsonian mount scope with a solid tube.
And of course, having completed that project, another one is now underway. The newest instrument, also being totally built from scratch, is to be a 20.1 inch ultra-light AltAz mounted truss scope with a computer drive system.
For additional details on these scopes, click in the links underlined above.
For more information on Amateur Telescope Making, and how to get started in this fantastic hobby, see the ATM links on my homepage (click below).
