Re: [ATM] Spider vane color? : Against the vane

[Kevin MIchael Zabbo <chaosopher23@yahoo.com>]

Why not dispose of the vanes altogether, and make
either a refractor, a TCT, or use an optical window to
fully enclose the optical business-end so that the
diffraction effects are nice and round and minimized? 
I hear that the Stevick-Paul configuration is really
nice for the TCT option, and not all that hard to
make.

Kevin

--- Scott Ewart <scotte@frontiernet.net> wrote:

> Doug,
>     I tend to agree with Don.  The smoother and
> shinier, the better. 
> Scatter is what you want to avoid and in my opinion
> will be more 
> harmful.  Consider the moon 2 deg. off axis.  The
> light reflected off 
> the vane will hit the mirror or right next to it,
> but will be 
> reflected onto the side of the tube or back out the
> top away from the 
> secondary.  I think even flat black  will scatter
> more light directly 
> into the eyepiece.
> 
> Scott Ewart
> 
> 
> ----- Original Message ----- 
> From: "Don Clement" <clement.focuser@verizon.net>
> To: <atm@atmlist.net>
> Sent: Thursday, May 04, 2006 4:22 PM
> Subject: Re: [ATM] Spider vane color?
> 
> 
> I wonder if the best thing would be to leave the
> polished finish on 
> the SS
> spider vanes. Reflected light from the spider vane
> sides would be 
> diverted
> harmlessly outside a truss or onto absorbing sides
> of a tube wall. An
> example is a 3" to 2" adapter I make. The lower ½"
> of the 1" long 
> adapter is
> smooth sided 45 degree cone. Light is reflected from
> the smooth sides 
> of the
> adapter into the deep internal pleats of a flat
> black bellows. The 
> result is
> almost total absorption of the reflected light by
> the light trapping 
> pleats
> of the bellows. When looking up into the adapter the
> surface appears 
> more
> black than any thing I have experienced. The
> reflective cone and light
> trapping pleats is blacker than even good black
> velvet surface.
> 
> 
> 
> Don Clement
> 
> Running Springs, California
> 
> 
> 
> > I'm rebuilding a 6", and I've made a spider from
> 0.005 inch
> > stainless shim stock, 1/2 inch wide. It makes
> GREAT vanes
> > -- very thin, very strong. BUT -- of course,
> they're
> > polished stainless, but I hesitate to paint them
> black. I'd
> > have to rough them up (not easy to do smoothly),
> and they'd
> > end up thicker. And, at only 5 mils, paint will
> > substantially thicken them. The spider is in a
> full tube,
> > so they can't really reflect any light anywhere
> interesting
> > - so I think leaving them bare is best.
> > Suggestions/recommendations from the group??
> > Doug
> >
> >
> > _________________________________
> > Dr. Douglas N. Arion
> > Hedberg Distinguished Professor of Entrepreneurial
> Studies
> > Professor of Physics
> > Head Coach, Ice Hockey
> > Carthage College
> > 2001 Alford Park Drive
> > Kenosha, WI 53140
> > 262-551-5864
> > 262-551-6208 (Fax)
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