Re: Graticule for Leica stereo eyepiece

On May 3, 9:55 pm, Richard J Kinch <ki...@xxxxxxxxxxx> wrote:
JB writes:
Is field number the same as field of view?

The field number of an eyepiece is the number of millimeters in its field
of view, which is typically stopped by a field stop, in this case the
flange you're measuring inside the eyepiece as 18.5mm.

Now the definition of magnification means that a 18.5mm field seen in an
16X eyepiece appears to be an object of size 16*18.5mm = 296mm at a
standard reading distance of 10 inches = 254 mm. The apparent half angle
of that view would be arctan(0.5*296/254) = 30 deg, so the angular full
field is a whopping 60 degrees across. A typical wide-field eyepiece is
about 40 degrees. Does the field really look 60 degrees wide in the
eyepiece?

Field of view is never, ever given in mm's

Thanks,

Kevin Cunningham
SMS
.

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