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deSitter
Carpal Tunnel
Reged: 12/09/04
Posts: 2926
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Can anyone do this simulation? Say three threaded rods radially to a spider. the complication is that the edges of the rod are not oriented radially anywhere. My gut feeling is that this will spread out the diffraction spikes over equivalent solid rods. thanks in advance.
-drl
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sixela
Postmaster
Reged: 12/23/04
Posts: 10848
Loc: Boechout, Belgium
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Threaded rods are thick.
How the energy is spread is the least of your worries: your worry is that there *is* a lot of energy spread, at least compared to what a thin vane spreads.
I haven't computed the point spread function, but my guess is you'll have six main spikes with some secondary spikes aligning with the threads on the rods.
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400mm f/4.46 self made Dobsonian on Tom Osypowski equatorial platform
Orion Starblast (114mm f/4 reflector, Alt/Az)
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Luigi
Post Laureate
Reged: 07/03/07
Posts: 4933
Loc: MA
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Easy enough to try it and see what you get. Let us know. I'm guessing it won't be pretty. 
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17.5" f/5 Dob. IM-715 MCT. 120ED. Lunt 60mm Ha.
Zeiss, Leica, Fujinon, Nikon, Pentax, Bushnell bins
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deSitter
Carpal Tunnel
Reged: 12/09/04
Posts: 2926
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Well I have a telescope to repair and this is a first cut. If the telescope cuts it optically, the threaded rods will be replaced by thin smooth ones - unless the threaded ones actually perform better! Vanes are unfortunately not an option, or at least I haven't thought of a way to do them yet.
-drl
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Mert
Carpal Tunnel
Reged: 08/31/05
Posts: 1788
Loc: Spain, Pamplona
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Why don't you use thin steel guitar strings?
They're very strong and relatively cheap.
2 per "vane" with a short distance between them
could be doing fine I believe 
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Mert
42º49"N 1º38"W
3" Polarex refractor
6" F12 SW Maksutov,CS2-S
EQ6 + EQMOD 
SPC900NC/DFK21AU04.AS
My web-page don't laugh, I should make it better!
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mark cowan
Vendor (Obsidian Optics)
Reged: 06/03/05
Posts: 2156
Loc: salem, OR
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The primary spikes will be bright and short, with small amounts spread orthogonal to the thread shadows. I have a long piece of 1/4" threaded waiting to try a bench test of this very thing, to illustrate the diffraction patterns of various materials often suggested - yarn (wooly edges to vanes), threaded rod, etc. - it's difficult to model such stuff directly.
Best,
Mark
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