From: "Mel Bartels" 
To: 
Reply-To: "Mel Bartels" 


>>>
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?
<<<

Quick BOE calculation shows amount of light many magnitudes less, unless
very bright object like the Moon is just the correct distance off-axis.
However, others and I have proposed the idea that some of the surprising
improvement that wire spiders give is the lack of boundary layer of air
that stabilizes with different index of refraction.  That needs to be
tested.

Mel Bartels

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