From: "Richard F.L.R. Snashall" 
To:  atm{at}shore.net
Reply-To: "Richard F.L.R. Snashall" 




Jerry Hudson wrote:
> To ol' Coyote -
>
> Your formula,
>
>> a*rho^2+b*rho^+b*rho^4...
>
> giving the shape of the Schmidt plate, is
> exactly opposite in sign to the wavefront
> aberration describing an uncorrected spherical
> mirror.  The glass introduces just enough extra
> path length where it is thicker to compensate.
>

In fact, Kingslake uses this exactly.  Couched in the latter part of the proof:

        "Along the axis this optical path is
        evidently (nt+r+a).  Equating these.."

I was slightly taken back when I saw this.  Don't know why, just was.

                Rick S.

--- BBBS/NT v4.00 MP