Re: Field of View and Magnfication calculations

On Apr 20, 8:21 am, Dave Typinski <möb...@xxxxxxxxxxxxx> wrote:
Eugene <eugenhug...@xxxxxxxxx> wrote:

What has the thin lens formula got to do with it. I'm
inquiry about the formula for small angle where

theta subtended by object = arctan (object size/distance)

then apparent field of eyepiece like TV Plossl 50 degrees
divided by the theta is equal to the magnification.

Does this magnification calculations based on the theta
and Plossl field accurate when the object is 4 meters
away, 8 meters away, at infinity?

The calculation is accurate everywhere because for any given object of
interest--say, a meter stick--theta will change depending on the
object's distance from the observer.
--
Dave

But in using a compound system with primary and secondary
mirrors. Sometimes the focal length changes because you
are adjusting the rear visual back distance from the
secondary to focus close. Or is the calculation entirely
independent of the focal length of the system??

E
.

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