RE: ATM atm ground- to deep

[BOB PRABOWO <BOB@bahana.co.id>]

Hi Adams,

>       ground past my desired f ratio. Is there some grinding method to
lengthen        the f ratio ?   
Of course there is :-) Just grind with Tool On Top.

Here's the rule:
Grinding with Mirror On Top, will shorten the focal length. While
grinding with Tool On Top, will lenghten the focal length.

That's why once the desired focal length is achieved, you have to grind
MOT and TOT alternately (one wet of MOT followed by one wet of TOT) .

 If the focal length is too short, do 2 wets with TOT followed by one
wet with MOT, keep on doing this until the desired focal length is
achieved. Once it's achieved do the "normal" MOT - TOT.
If it's too long, grind two wets with TOT followed by one wet of MOT. 

What I did when my mirror was shorter than desired was, ground with TOT
for a several wets, checked the f.l, when it's still shorter, I did a
few more wets and finally after the sagitta was right I continue with
MOT - TOT. If you do this, don't forget to check the f.l after each wet.

Bob P. Sumitro
Jakarta, Indonesia
the new land of the free

"To be able to express your opinion freely, free of fear, ain't that
great!" 

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