# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Persistence and demise of Lunars
From: Bruce Cutting
Date: 2017 Dec 11, 11:10 -0700

```I've been following posts relevant to lunars and as a rank newbie have a
question.

tables (other than the standard almanac) are needed.  My understanding is
that you need tow bodies (likely the moon and the sun, but that other
bodies can be substituted for the sun).  You need a fair guess at the
observing latitude, date, and time, then use an iterative process to get
actual La and Lo.

I've heard it goes as follows:
1) measure the distance between moon and body (usually limb closest to the
sun or selected body)
2) measure the altitude of both bodies
3) Use the altitude of the Sun (or other body) and latitude to improve
guess at time.
4) using the guessed at time compute GP and altitude of both bodies and
the expected lunar distance
5) Iterate on the process until it converges.

So the questions are:
1) What tables are needed (if any)
3) Is a sextant accurate to minutes and seconds good enough to get
reasonable results?

> Another irony was that when the survivors stumbled across uninhabited
> Henderson Island halfway through their voyage, they were a mere 100 miles
> from a thriving English-speaking colony.  Their copy of Bowditch was not
> up
> to date.  Six years earlier, two British frigates had rediscovered
> Pitcairn
> Island, home of the descendants of the Bounty mutineers.  The information
> had yet to filter back to America and make it into Bowditch.
>
>
> Don Seltzer
>
>
> View and reply to this message:
> http://fer3.com/arc/m2.aspx/Persistence-demise-Lunars-Seltzer-dec-2017-g40877

```
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