Re: Re : ATM Prime focus

[Brian Nestel <blast@aloha.net>]

Robert C. Pfaff wrote:
> I went through all the optical books that I have and could not
> find a definition for PRIME FOCUS. If anybody can find a definition
> of prime focus in PRINT that would be very interesting. Please
> quote. If not then what we agree here is what it should be.
> Think about it.
Hi:
The defination of prime focus that I found in the "The Facts on file
Dictionary of Astronomy" follows:
prime focus- The focal plane in which the image of the primary mirror
or objective lens forms, in the absence of other optical components.

The "Amateur Astronomer's Handbook" by J.B. Sidgwick P.363, 20.11
makes the statement: "The obvious position for the photographic plate
is in the focal plane of the objective--the prime focus.

It is also refered to as the "Principal Focus" or "Principal Plane" in 
other optics manuals Which I won't quote to save bandwidth.
-- 
Aloha   159 36 W, 21 58 45 N
Brian   Middle of the Pacific,
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