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"Dr. Geoffrey Kolbe" wrote:
>
> I have a surveying theodolite, but there is no way of illuminating the
> cross hairs.


One old surveyor's trick for making Polaris observations at night is
to hold a flashlight just outside the field of view and shine it into
the telescope objective lens.

You can also place the tip of your index finger, illuminated by a
flashlight held in the same hand, so it protrudes into the field of
view. I like this method a little more, but either one is quite
effective for making the reticle visible without washing out the star.

Many theodolites have a small "lollipop" in the telescope, easily
visible through the objective lens. It's made of thin metal and is
normally turned edgewise. For crosshair illumination, you turn the
lollipop 45 degrees. That causes its round tip, at the center of the
telescope tube, to intercept a light beam supplied through the side of
the tube and deflect it back toward the reticle. The light comes from
the circle illumination optics, so the lamp and power source need to
be operating. Or you shine a flashlight into the illumination port.

Someone in the Sextants group may know more about this.
http://groups.yahoo.com/group/Sextants/

--


paulhirose@earthlink.net (Paul Hirose)

   

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