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Subject: Re: [Fwd: [Nml] Davis Sextants]
From: Chuck Taylor (ctaylor@XXX.XXX)
Date: Mon Jan 25 1999 - 11:56:15 EST
On Mon, 25 Jan 1999, carl wrote:
> The two major problems with the M25, are, 1) The full view mirror is
> difficult to use with stars as nautical twilight approaches (as has been
> noted--although it's fine for sun sights) and 2) the mirrors are very difficult
> to adjust--the mounts are too light so the act of adjustments causes the mounts
> to flex and the threads of the adjustment screws need to be finer to allow more
> precision.
With regard to problem #2 above: the power squadron I belong to owns
several Mark 15's and 25's and I've also examined several belonging to
others. The quality seems to vary from unit to unit. Some are pretty
good. On one there is simply not enough travel in the mirror adjustment
mechanism to adjust it properly. It just won't go far enough in the
required direction. Also, the adjustment screws have too much play. So
far I've only seen the one bad apple, but it pays to be careful when
purchasing one, whether new or used.
As for the optics, comparing the scope on a Davis sextant to the scope
on an Astra is like comparing the brightness of a 15 watt bulb to that
of a 100 watt bulb at 100 yards. The light-gathering ability (and hence
the brightness of the image) is more critical than the magnification
(IMHO).
Still, I tell my students that the Davis is plenty good enough to find
any port in the world and is a good learning tool for the price.
Chuck Taylor
Everett, WA
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