From: Mark Holm 
To: Dave Magee 
CC: atm{at}shore.net
Reply-To: Mark Holm 


Winspot is a ray tracing program.  Not what I was thinking of.  I need a
wave optics program.  Some aspects of the calculations are similar, but the
underlying theory and the results are very different.  Ray tracing has it's
uses, but many ATM's don't seem to realize it's limitations.  When you get
down to analyzing the effect of shape differences on the order of or
smaller than a wavelength of light, ray tracing just doesn't cut it.  Got
to go with wave optics.

Anybody knows that putting a really lousy diagonal between your precious primary
and Nagler eyepiece will muck up the view.  The question that has been
floating around the list is: What are the effects of merely mediocre
diagonals?  I think the answer, as provided by wave optics, is that you
predict the result exactly as you would for the primary, except that you
have to take the peculiar geometry
of the diagonal into account.  Others say things that are at odds with this
view.  I'd like to have a calculation mechanism that can be used to make
solid predictions from solid theory, and at the level needed, ray tracing
isn't good theory.

I made a crude wave optics program for calculating diffraction patterns
resulting from mirror cell induced warping as reported by Plop. (The
program was
crude only in that it used a very simplistic approach to performing the
calculations.  The  calculations adhered exactly to wave theory.)  I need a
version that can deal with the geometry of the diagonal mirror situation. 
I haven't yet figured out how to make it go.  I am sure the problem has
been solved by someone already, but don't know where to look.

Mark Holm
mdholm{at}telerama.com

Dave Magee wrote:

> Mark,
>
> Maybe you already have it, but here's a URL to get WinSpot. A free (nice
> word:-) spot plotter from Dave Stevick's TCT/ weird telescopes page. By the
> nature of the TCT group, they allow a lot of angle variations. They also let
> you have the source code, so you wouldn't have to sit down and start from
> scratch.
>
> http://bhs.broo.k12.wv.us/homepage/alumni/dstevick/software.htm
>
> /Dave
>
>
>>Now, I have to admit there are aspects of this argument that puzzle me
>>
> too, and
>
>>I am not sure I have it 100% correct.  I keep thinking I need to sit down
>>
> and
>
>>write a computer program that calculates path length differences for
>>
> different
>
>>diagonal situations and plots the resulting diffraction patterns.  That
>>
> would be
>
>>the most rigorous way to be sure of the predictions of wave optics.
>>Unfortunately I have to spend a lot of my time earning a living and doing
>>
> other
>
>>necessary things.
>>
>
>
>

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