Re: Longitude sight, South Pacific, 1864
From: Frank Reed
Date: 2018 May 14, 11:44 -0700
Two things. You wrote:
"The total of the logs is 19.33631, dropping the tens is 9.33631"
Tricky issue here... Try this: divide by two first. Then "reject the tens".
And you wrote:
"The scrap shows LAT= 05:44:40"
Simple issue here... You accidentally copied over the chronometer time. The local time is 3:42:04. That should fix things up, right?
By the way, your latest post highlights one other source of confusion worth knowing about. You used "LAT" for local apparent time. Historically, this acronym was not used, and if you teach this process today you'll discover one reason why we might want to avoid it today. It's easily confused with "Lat" for latitude. Now for those of us with math or engineering or science or other tech backgrounds, we are alert to the fact that "LAT" and "Lat" are not the same thing because the letters are different cases --therefore different meaning (how long ago did this become natural for us? ...both individually and collectively?). But in the rest of the universe, this distinction by case is trivial and confusing. Many people today routinely take notes in all upper case letters (if they take notes at all). They will record their notes as they're accustomed to, no matter what you say. If you ever find yourself in a scenario where you're trying to explain this methodology to non-experts, avoid "LAT"! And back then, this was just "time" (or sometimes "local time" or frequently "true time"). I also prefer to call it "sundial time," as you know, since that's a type of time that non-experts can relate to, and that is in fact what we are measuring with these sights. A "time sight" turns a sextant into a highly accurate sundial.