Re: [ATM] Thin Titanium Spiders & Diffraction Spikes

[Kevin Whitefire <chaosopher23@yahoo.com>]

I would think that if you want to max out on contrast
and keep those spikes away, and don't feel like
replacing guitar strings every few weeks, an optical
window is the way to go.  No spikes, no vames to
adjust, no guitar strings to tune and replace.

A window 1/2" thick for a Newtonian 8" diameter should
be about right, but this can get expensive for large
apertures, such as a 16" monster.

Kevin
--- artbianconi@blast.net wrote:

> Jim, Thanks for the response. Let me tease the
> example you gave 
> so I can project the theory some.
> 
> If a thinner spider of a given length, generates
> less of Huygens 
> wavelets than the same spider when it's thicker,
> that suggests 
> that the diffraction we see is a function of surface
> area of the 
> spider exposed to the incoming image.
> 
> If that is correct, then a curved spider that has
> the same 
> projected surface area will generate the same number
> of Huygens 
> wavelets as a conventional one. However, because it
> is curved, 
> the distribution of those wavelets is more uniformly
> distributed 
> over the image field and the effect on contrast is
> thus not as 
> apparent. The degradation is still there, but it's
> not obvious.


=====
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