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Re: Sextant arc length
From: Brad Morris
Date: 2015 Sep 17, 16:26 -0400
From: Brad Morris
Date: 2015 Sep 17, 16:26 -0400
Hello Stan
Heath Hezzanith Endless Tangent Class A sextant from about 1923. Top of the line, top of the mark sextant with all the trimmings, including the binocular attachment.
Greatest mark on the arc. 150°
Greatest measurable angle 128°
The vernier is exactly 20°, so when the index is set at 128°, the last vernier mark is 148°.
Brad
On Sep 17, 2015 3:07 PM, "Stan K" <NoReply_StanK@fer3.com> wrote:
From what I have read, it looks like the Navy Mk II could measure to its final marking of 145º. If you have one, please check this for me.
Stan
-----Original Message-----
From: slk1000 <slk1000---.com>
To: navlist <navlist@fer3.com>
Cc: slk1000 <slk1000---.com>
Sent: Wed, Sep 16, 2015 3:16 pm
Subject: Sextant arc length
What is the largest usable angle that any standard marine sextant you know of can measure? I have one where the arc is marked to 150º, but the index arm hits the horizon shade bracket just shy of 130º.
I put limits on just about everything in my Celestial Tools program, so ridiculous entries are automatically flagged, e.g. limiting longitude to 180º. In the earlier versions of Celestial Tools I limited the degrees of sextant altitude to 140. In V4.2.0 I changed it to 150, then back to 140 in V4.4.0. This morning I was looking at a 1977 Bowditch and found a back sight problem where the sextant altitude was 141º04.9'.
It is easy enough to change Celestial Tools, but now I am curious to know what is actually out there. Looking at a bunch of old Celestaire catalogs, the largest arc I can find is only 135º, which I have to believe is a usable angle. What do your sextants have?
Stan
