Re: [ATM] Re: ATM Digest, Vol 17, Issue 10

["David Harbour" <scarab2@cox.net>]

Arjan,

I have confidence in you as a mathemetician, but the value seems to awfully
high, to me.

Dave

On th eother hand, it really is a giant.


----- Original Message ----- 
From: "Arjan te Marvelde" <arjan.te.marvelde@hetnet.nl>
To: <atm@atmlist.net>
Sent: Tuesday, May 10, 2005 2:16 PM
Subject: [ATM] Re: ATM Digest, Vol 17, Issue 10


> > I also toured the Hobby-Eberle.  Here's a puzzle (one the guide couldn't
> > answer).  Its primary is an 11 meter f/1.5 sphere.  How much difference
in
> > sagitta would there be if it were a paraboloid? (answer withheld as an
> > exercise for the reader, and also because I haven't figured it out yet)
>
> Equivalent formalae (equal paraxial ROC = R) would be:
> sphere:     x^2 + (y-R)^2 = R^2, or y = R - sqrt(R^2 - x^2)
> parabola:  y = (x^2)/2R
>
> so for x = radius = 5.5m and R = 33, the sag would be
> sphere:    929.8 mm
> parabola: 458.3 mm
>
> This deduction may, of course, be wrong.
>
> Cheers
> /Arjan
>
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>


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