Sky @ Night Magazine - Build a telescope

Share practical advice and tips on making your own kit

RE: Sky @ Night Magazine - Build a telescope

Postby brijm » Sat Feb 23, 2008 6:13 pm

Has anyone actually tried building it yet? By my calculations this bench seems to have been designed with pygmies in mind - it is just over 60 cm tall. Am I missing something?
brijm
 
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RE: Sky @ Night Magazine - Build a telescope

Postby thebest » Mon Feb 25, 2008 1:03 am

[quote]ORIGINAL: brijm

Has anyone actually tried building it yet? By my calculations this bench seems to have been designed with pygmies in mind - it is just over 60 cm tall. Am I missing something?

[/quote]
What you're not a pygmie like the rest of us????
i got to agree, was rather silly...i nearly dropped the magazine in shock
thebest
 
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RE: Sky @ Night Magazine - Build a telescope

Postby ajohn » Mon Feb 25, 2008 6:00 pm

There's an old book that may be about and aught to be reprinted if it isn't. It's called "how to make a telescope" by Texereau. Translated from French many moons ago. He's the man that made Plossl eyepieces famous. There are 2 books one just deals with newtons the other cassegrains too. It's worth while read for people who don't actually want to make a mirror as well. It contains a fair amount of information on telescopes in general. Going on some of the responses from people on the telescope I have on sale on here many people really do need to read it. It also has some info on the problems of photography through a telescope. Dated maybe but substitute pixel size for grain size. The problems are the same.

The book is also the only complete account I have ever seen on what can be achieved with a Foucault tester. I've seen loads and loads of them over the years.

There is another one that is bound to be out of print. (Cant lay my hands on it either) All it really adds concerns mirror making. That's finish grinding and polishing with the mirror up to maintain a clean edge. A practice frowned on by many but having gone through it I just have to agree. It also mentions using plastic large meshed draining board covers and fine and other mesh to alter the surface of pitch laps breaking it up to improve contact and polishing action. Also cutting channels in laps rather than sticking on squares as Texereau suggests. A tenon saw works well.

I've seen comments on here to the effect that is isn't worth making a mirror on cost grounds. Well I would suggest that people get a quote for a 1/10th wave peak to valley mirror that hopefully has no ripple. They might be in for a shock and may even be able to do better if they did it themselves. Have to agree though coating does seem a mite expensive but I did discover about 5 years ago that as a one off a 10ins mirror uses about £20 worth of materials. Ok some one who is doing it all the time can reduce that but-.

John
[:)] On the bench I did find it best to sit down while testing but would agree that it's too low for grinding and for assembling bits even if the scope uses a bought mirror.
ajohn
 
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