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--- george huxtable wrote:

> I think Davis have produced several widely-different
> grades of plastic
> sextant, though I am familiar with none of them.

In the course of teaching celestial navigation courses
for the U.S. Power Squadrons, I have had the
opportunity to examine more than a few Davis plastic
sextants (maybe about a dozen different examples).  My
observation is that they vary in quality, even within
the same model.

Specific defects that I recall seeing include:

1. A horizon mirror for which the adjustment screw
lacked enough travel to bring the mirror into proper
adjustment.

2. A drum vernier with obviously unequal spacing of
the calibration lines.  (The local dealer exchanged it
for a better one.)

Most seem to be reasonably well-constructed.

Starpath has a discussion about and pictures of the
currently available Davis plastic sextants on their
web site:

http://www.starpath.com/catalog/accessories/psextants_midpage.htm

See also

http://www.celestaire.com/catalog/Marine_Sextants/Davis/

David Burch has written a detailed description of the
use of plastic sextants (as has been mentioned before
on this list):

http://www.starpath.com/online/celestial/plastic.pdf

--
Chuck Taylor
North of Seattle, USA


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