Any Amateur Telescope Makers?

[johnniet]

I've gotten obsessed with optics recently. Not just looking at different telescopes or cameras, but wondering what the difference really is between an Erfle, a Ploessl and a Nagler.
Why do roof prisms have to have such tight tolerances.
How do you know which two lenses to put together to make an achromat, and why.
How much magnification would I need to see some features on Mars?
I've wasted lots of hours reading online sources...haven't yet sprung for the books.
Does anyone here actually know this stuff?

 

[Cougar Allen]

I've messed around a little. The Amateur Astronomer's Handbook by James Muirden is great and your local library probably has a copy. It gives directions for grinding acromats as well as mirrors, and diagrams of the various eyepiece designs.

 

[toolmaker]

We have manufactured components for telescopes, radars, infrared systems, etc. The reason for the tolerances are to reduce interference from internal causes, increase resolutions, more reliable targeting systems, etc.

 

[johnniet]

Originally posted by toolmaker
We have manufactured components for telescopes, radars, infrared systems, etc. The reason for the tolerances are to reduce interference from internal causes, increase resolutions, more reliable targeting systems, etc.

Well, of course.
But why are roof prisms so fussy compared to porros?

 

[jrollins]

Sounds like it's time for someone to go to the library! I don't know much about telescopes, and I don't really want to make my own mirrors and lenses. That's just too much work. What I wouldn't mind so much is buying all the parts to make one, but I don't want to spend the money. Then again, I don't want to spend the money on a factory built model either... So I'm stuck with a few really small cheap telescopes that I can't see much through.

 

[johnniet]

Jrollins,
you do not have to make your own mirrors and lenses.
There are many sources of surplus optics on the internet.

The one I'm most used to is www.surplusshed.com
You might try using some of the cheap lenses first (under "educational optics") just to figure out how you want to set things up.

Another one is http://www.apogeeinc.com/
There's also www.sciplus.com

There's a lot of information at the "Astronomy Daily" site; this is their faq on telescopes:
http://www.astronomydaily.com/faq.asp#scopes

They even have some ideas about how to improve your department store scope.

Remember that a used scope is also an option. You can look on ebay (after doing a lot of research) or you can check out classifieds, like
www.astromart.com

You can do the research at
http://www.scopereviews.com/
http://www.findascope.com/

 

[Steve Hayden]

Simple newtonian reflectors are what most amateur astronomers start with when building their own scope.

If you are going to the trouble to build your own refractor, I suggest that you skip the achromatic objective and build one with an apochromatic triplex objective. If you can afford it, low dispersion glass or fluorite lenses will make the best.

Ploessel eyepieces are generally four lens combinations while erfles are wider angle multi-lens combinations-usually 6-7 lenses. There are several brands of eyepieces now that use low dispersion glass or fluorite lenses at fairly reasonable prices

Unless you can afford phase coatings, try to get a polished aluminum mirror rather than prizm tpe star diagonal.

All this aside, if you think the knife habit is expensive, you are in for a revelation. Optics can become an amazing money pit.

 

[johnniet]

Where do you get fluorite lenses?

And what exactly are phase coatings? I know they double the price of a pair of binoculars.

 

[Steve Hayden]

Prizms split light into the spectrum and phase coatings are used to correct for this. Using a mirror type diagonal will compensate for this as it won't split the light into components.

I am not sure where to get fluorite lenses. I would search the net, but personally would try to locate an apochromatic objective already assembled to construct the telescope with. The objective will probably run as expensive as a cheap refractor, but the end result will be worth it.