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Equipment Discussions >> Refractors

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Rich V.
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Reged: 01/02/05

Loc: Lake Tahoe area, Nevada, USA
Re: OTA material: Aluminium or Kruppax 50? (thermals) new [Re: Mark9473]
      #5658282 - 02/02/13 02:40 PM

Thanks, Mark, I wasn't aware that scope had a Kruppax option. I thought only the LZOS lensed models came that way...

Currently I can only find this aluminum 107/700 on the APM site:

APM 107/700 w/2.5" focuser

Your scope sounds like a nice combo.

Rich


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Mark9473
Postmaster
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Reged: 07/21/05

Loc: 51N 4E
Re: OTA material: Aluminium or Kruppax 50? (thermals) new [Re: Rich V.]
      #5658373 - 02/02/13 03:37 PM

I tapped the tube with a large screwdriver just to make sure; doesn't sound metallic. Is that conclusive you think?

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Rich V.
Post Laureate
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Reged: 01/02/05

Loc: Lake Tahoe area, Nevada, USA
Re: OTA material: Aluminium or Kruppax 50? (thermals) new [Re: Mark9473]
      #5658514 - 02/02/13 05:00 PM

You've got me!

Both my refractors have heavy alum. tubes; they make a dull "thunk" when tapped; not tinny but still metallic, I suppose. The tubes get frosty but the lenses haven't ever dewed, though. Eyepieces and Telrads are more problematic, though.

Not exactly a definitive test, I suppose...

Rich


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GHarris
super member


Reged: 06/06/09

Re: OTA material: Aluminium or Kruppax 50? (thermals) new [Re: Rich V.]
      #5660058 - 02/03/13 02:08 PM

Thanks for all the helpful advice. I opted for the Kruppax tube in the end.

Since I'm having the OTA custom-made now (the Kruppax version of the scope is not quite off-the-shelf like the aluminium OTA) I've sent myself into a dither over whether to choose a standard tube length or a shortened one for binoviewing. If anyone wants to slam my naivety the thread is over in the Binoviewers forum


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Mike Clemens
Frozen to Eyepiece
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Reged: 11/26/05

Loc: Alaska, USA
Re: OTA material: Aluminium or Kruppax 50? (thermals) new [Re: GHarris]
      #5660759 - 02/03/13 09:21 PM

I built all mine with 8-9" of in-focus for unbarlowed binoviewing with a mirror diagonal. NO regrets.

http://www.pbase.com/mclemens1969/image/68819908
green = 2" diagonal optical path length
gray = binoviewer path length
purple = light cone


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Mirzam
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Reged: 04/01/08

Loc: Lovettsville, VA
Re: OTA material: Aluminium or Kruppax 50? (thermals) new [Re: Mike Clemens]
      #5661237 - 02/04/13 07:43 AM

Definitely give yourself the option for binoviewing. IMO it's the best way to critically view the Moon and planets, and not by a small margin.

JimC


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Jeff B
Carpal Tunnel
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Reged: 12/30/06

Re: OTA material: Aluminium or Kruppax 50? (thermals) new [Re: Mike Clemens]
      #5662125 - 02/04/13 05:01 PM

Quote:

I built all mine with 8-9" of in-focus for unbarlowed binoviewing with a mirror diagonal. NO regrets.

http://www.pbase.com/mclemens1969/image/68819908
green = 2" diagonal optical path length
gray = binoviewer path length
purple = light cone




A big +1 from me. I build ALL of my refractors this way. With F7 and slower scopes, there's no real reason not to.

Jeff


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