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Rich V.
Post Laureate
Reged: 01/02/05
Loc: Lake Tahoe area, Nevada, USA
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Re: OTA material: Aluminium or Kruppax 50? (thermals)
[Re: Mark9473]
#5658282 - 02/02/13 02:40 PM
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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
Reged: 07/21/05
Loc: 51°N 4°E
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Re: OTA material: Aluminium or Kruppax 50? (thermals)
[Re: Rich V.]
#5658373 - 02/02/13 03:37 PM
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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
Reged: 01/02/05
Loc: Lake Tahoe area, Nevada, USA
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Re: OTA material: Aluminium or Kruppax 50? (thermals)
[Re: Mark9473]
#5658514 - 02/02/13 05:00 PM
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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
member
Reged: 06/06/09
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Re: OTA material: Aluminium or Kruppax 50? (thermals)
[Re: Rich V.]
#5660058 - 02/03/13 02:08 PM
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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
Reged: 11/26/05
Loc: Alaska, USA
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Re: OTA material: Aluminium or Kruppax 50? (thermals)
[Re: GHarris]
#5660759 - 02/03/13 09:21 PM
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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
Post Laureate
Reged: 04/01/08
Loc: Lovettsville, VA
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Re: OTA material: Aluminium or Kruppax 50? (thermals)
[Re: Mike Clemens]
#5661237 - 02/04/13 07:43 AM
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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
Reged: 12/30/06
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Re: OTA material: Aluminium or Kruppax 50? (thermals)
[Re: Mike Clemens]
#5662125 - 02/04/13 05:01 PM
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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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