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Equipment Discussions >> Reflectors

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careysub
Carpal Tunnel
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Reged: 02/18/11

Loc: Rancho Cucamonga, CA
Re: Secondary spider designs? new [Re: Starman1]
      #6107696 - 09/29/13 03:02 PM

Quote:

...
I would like to experiment with the )(-shaped spider like on the 12.5" Obsession. It's been rigid enough on the scopes I've seen with that design (some 8" and 10" scopes), and it seems fairly rigid when tightening collimation screws (perhaps a little better than the 4 straight vanes I'm used to). If anyone out there has a 12.5" Obsession, I'd like to know the thickness of the vanes.




I wonder if spiders that look like this OO (two complete rings) would work using spring steel strips. They would be under tension, and (I think) resistant to vane twisting*. Would the tension make the hoops stiffer?

*A limiting factor in using wide, thin vanes is that unless the vanes are perfectly parallel and perfectly aligned with the optical axis the profile is likely to be much larger than the vane thickness. A 1" wide, 0.01" thick vane will have its profile doubled by a tilt to the optical axis of just 0.57 degrees.


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Sarkikos
Postmaster
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Reged: 12/18/07

Loc: Nyctophobia, Maryland, USA
Re: Secondary spider designs? [Re: careysub]
      #6108115 - 09/29/13 08:06 PM

The Edmund Astroscan and Bushnell Voyager, both 4.5" reflector ball scopes, have an optical window instead of spider vanes.

Mike


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