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camvan
Carpal Tunnel


Reged: 05/02/05
Posts: 2142
Loc: British Columbia
creating a folded refractor...
      #1504492 - 03/25/07 05:43 AM

we have an ETX 60 AT and the focusing mechanism kinda just went wonky on us. we opened it up to see what was wrong...can't figure it out. we're not overly worried as we haven't used it for about 2 years now. but, with some members in our association being interested in perhaps sitting down and grinding some mirrors for a few ATM projects, I thought of the folded refractor thread.

I know have a 60mm F5.8mm achromatic lens. this means I have some fun for the heck of it

I'm wondering what idea's you might have for me? worth trying to make a folded refractor? perhaps I should get a good ep and try to make a spotting scope?

I'm ready to entertain some thoughts and suggestions, if any of you are willing to offer

--------------------
Cameron

"Aperture can only be replaced by even more aperture. Dark transparent skies cannot be replaced by anything else." - Stathis Kafalis

Intes MN66
Meade SN8
handfull of cheap ep's


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Alan French
Night Owl


Reged: 01/28/05
Posts: 4009
Loc: Upstate NY
Re: creating a folded refractor... new [Re: camvan]
      #1504772 - 03/25/07 10:33 AM

We had one of the ETX 70 ATs here because the focuser wouldn't work. The owner had pitched it over onto the lens end fairly hard. IIRC, there is a rod that moves the lens assembly itself in and out, and the little retaining clip that held the rod near the base of the tube had gotten pushed up the rod and was no longer holding the rod. Instead of moving the lens, the focuser knob was moving in and out of the back end of the instrument. A major disassembly of the mount was required to get at the tube innards.

I was able to fix it.

Clear skies, Alan


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Jon Isaacs
Postmaster


Reged: 06/16/04
Posts: 32442
Loc: San Diego, California
Re: creating a folded refractor... new [Re: camvan]
      #1504874 - 03/25/07 11:10 AM

Hi:

I think Alan gave you some good advice on fixing your scope, that would be my recommendation.

Folding a refractor makes sense if the focal length is 60 inches because it turns a 60 inch long scope that requires a big mount into a scope maybe 30 inches long and much more useable. With a scope that is arond 10 inches long it doesn't make a lot of sense. Folding also requires very good quality mirrors to avoid reducing the image quality.

Jon

--------------------


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Jeff Morgan
Post Laureate


Reged: 09/28/03
Posts: 4018
Loc: Prescott, AZ
Re: creating a folded refractor... new [Re: camvan]
      #1506150 - 03/25/07 11:26 PM

Quote:

I know have a 60mm F5.8mm achromatic lens. this means I have some fun for the heck of it

I'm wondering what idea's you might have for me? worth trying to make a folded refractor? perhaps I should get a good ep and try to make a spotting scope?




That is not a lot of focal length you have to play with, but I'm sure it would be a good learning experience. That is to say, Add money, Stir, Start over. Seriously, I have done the layout for a WO 80mm f/6 APOgrade which I have sitting on a closet shelf. The result is *real* short. Defintely a "table top" type of scope. After I get the 4" f/14 up and running I may give it a go.

--------------------
Jeff Morgan
Prescott, AZ
Wile E. Coyote School of Telescope Making


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camvan
Carpal Tunnel


Reged: 05/02/05
Posts: 2142
Loc: British Columbia
Re: creating a folded refractor... new [Re: Jeff Morgan]
      #1506158 - 03/25/07 11:29 PM

I apologize, I thought the idea of the folding refractor was to lengthen the FL (not to just lower the actual apparent FL.

back to the drawing board!

--------------------
Cameron

"Aperture can only be replaced by even more aperture. Dark transparent skies cannot be replaced by anything else." - Stathis Kafalis

Intes MN66
Meade SN8
handfull of cheap ep's


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