RE: ATM Some Telescope Making Parameters Question

[Andy Saulietis <iss@pvtnetworks.net>]

>That is what I called the radian method. Still, it's
>not clear to me why it works.


One radian is the angle (~57.3 deg) you get when  the length of
the arc equals the radius of the arc. So the exact angle of one radian
is 360/2*Pi degrees, or about 206265 arc seconds. For small angles
the field stop is ~ the length of the arc, and the radius is
the focal length. There are lenses made called 'f-theta'
design that approximate this very closely,  these are used for
applications that require a linear (constant) distance-to-angle conversion
factor.




Andy Saulietis
ISS Enterprises
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