From: "Richard Schwartz" 
To: "Vladimir Galogaza" ,
        "ATM shore" 
Reply-To: "Richard Schwartz" 


The trick here is that for a given star only a tiny spot of the diagonal is
used.   Surface errors beyond the boundaries of that spot are meaningless.
So the diagonal can be badly warped, but will still function well if it has
a smooth curve, as was shown by Anthony Stillman.   I am looking at having
a
minimum obstruction scope with the diagonal just far enough from focus to
avoid seeing the dust on it.   A relay lens or gregorian secondary will
re-form the image where it can be accessed by eyepieces.

. . . Richrad
Is Saddam alive?

----- Original Message -----
From: "Vladimir Galogaza" 
To: "ATM shore" 
Sent: Tuesday, April 01, 2003 2:11 AM Subject: Re: ATM How Good Does a
Diagonal Need to Be?


>
> >I am wondering if the quality required in a diagonal depends on the
> >distance from the diagonal to the focal plane.   If the diagonal is very
> >close to the focal plane, perhaps error in the diagonal surface can't do
> >much damage....
>  >. . . Richard
>
> Reading this and subsequent discussion I wander if, taking into account
> statistical nature of surface error  numbers ( Strehl, RMS, PV)
> these are linearly additive for two or more subsequent mirrors or some
other
> relationship has to be used to determine  final   error resulting from
> individual errors.
> ( James?)
>
> Vladimir.
>
>
>
>
>

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