From: "at making" 
To: rsackett00{at}yahoo.com, atm{at}shore.net
Reply-To: "at making" 


Hi,

An intresting to test is the impact of the black painting on spider. It
seems to be better to make the spider and secondary holder with stainless
steel for example and polish it . I know that it may sound strange but I
now use this kind of spider on my scope after a friend who know optics very
well speak to me about that and it's visible in Andr‚ Couder text, sorry,
in french :

http://astrosurf.com/altaz/effetthermique.htm



Fr‚d‚ric G‚a
http://astrosurf.com/altaz/index_e.htm


>From: Ross Sackett 
>Reply-To: Ross Sackett 
>To: atm{at}shore.net
>Subject: ATM Spider diffraction+reflection?
>Date: Thu, 19 Jun 2003 05:51:24 -0700 (PDT)
>
>
>Hi, all
>
>Following up on the interesting discussion on wire
>spider diffraction, I wonder if someone can help me
>think through this.  While I have no reason to
>challenge the idea that most of the light in
>spider-induced spikes is from diffraction, is some of
>it likely to be from low-incidence reflection off the
>spider vanes/wires as well?  We all know that at
>grazing incidences even the blackest coatings still
>reflect a considerable portion of the light.  At first
>thought shouldn't this light also spread in a spike
>perpendicular to the axis of the vane, just as
>diffraction does?  Any guesses as to the magnitude of
>reflection compared to diffraction effects?  And would
>wire spiders have a reflection advantage over wide
>flat vanes?
>
>Ross
>
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