From: "Dwight K. Elvey" 
To: atm{at}shore.net
Reply-To: "Dwight K. Elvey" 


>From: "Aditya Munshi" 
>
>Hi everyone,
>
>
>I am almost done correcting my 8" f/7 to a sphere. There is almost
>nothing left if the TUE only a central hole persists ? What I would like
>to know is how do I measure the magnitude of the central depression and
>how much can I correct in the final figuring ? Would it be advisable to
>correct the surface to a sphere now or to merge the hole into the
>parabola itself ?
>
>I need your thoughts on this
>
>Thanks
>
>Aditya

Hi
 If the hole is large enough to be out of the secondaries
shadow ( consider the widest angle you'll be using ). I'd work to remove
it. It is very difficult to smooth down a step edge while trying to
parabolize. That is why we start from a smooth sphere first.
 If it is completely in the shadow, it will cause little
problems.
Dwight

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