NavList:

Brad, you wrote:
"My Heath Hezzanith has just that feature, a small squib of white embedded in the handle, for taking notes. Yes, it is a metal sextant, from about 1920."

Aha. It's in the handle. That makes sense since, presumably, it's wood.

You added:
"Of course, that Heath has every feature known to man. ;-) Some useful, others….not so much. It has those ridiculous binoculars, they attach to the sextant in the same place as a telescope. Have fun swinging the arc with those! My nose always gets caught and it hurts, ouch!!!! "

Hmm. I suspect from this that you swing the arc the "modern" way which is not necessarily a good idea. I'll get into this in a separate post. I probably won't have time to get back to that this week, so for now, I'll do something that I don't normally like to do and point you to the archive: http://www.fer3.com/arc/m2.aspx?y=200510&i=026060

And you wrote:
"The other question was regarding back sights in actual practice. Bowditch talks to them as do others. But as you have proven, that doesn’t resolve the question of practice at sea. Have you ever encountered a back sight observation in your log traversal? Or are they as rare as a snowflake in Tahiti?"

I remember a long time ago seeing one specific case of a back sight in a logbook. I don't recall any details but it was little more than "got the latitude by back sight" when they were near land and there was no horizon beneath the Noon Sun. This was apparently the only significant use of back sights in practical navigation. I think someone, George?, suggested in a post that back sights were originally added to octants "for lunars". Since as George has mentioned it's very hard to get an index correction for back sights, which is true, this was clearly not the case (though it may have been suggested back then by someone who wasn't thinking through the practical aspects). Back sights were not used for lunars.

You've noticed back sights described in Bowditch probably in your 1849 edition. This is almost certainly not relevant since many sections of Bowditch were completely unchanged after the original edition of 1802. Even in 1880, you would find exactly the same archaic description of the octant that he wrote up nearly 80 years earlier.

From everything I have seen, back sights were over and done with by the early 19th century at the latest. That doesn't mean you wouldn't find them on instruments. As I have said, there is powerful design inertia among these instruments.

-FER

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