# NavList:

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

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Re: Lunars: Jupiter's BIG.
From: Frank Reed CT
Date: 2003 Dec 29, 18:51 EST
Fred you wrote:
"If the error of the chronometer were increasing exponentially, I would
rather have the instantaneous rate than the average rate...."

In that case, I think *I* would rather have a new chronometer! Seriously, in practice, if you had reason to believe your chronometer's error was increasing exponentially, you should use it as a paperweight. And in practice, chronometers' rates did not have that kind of nasty behavior.

By the way, you may recall we got started on this side thread because you (I think it was you) suggested that you could rate your chronometer by doing a couple of lunars in a row. That doesn't work because lunars are not accurate enough in most cases compared to the likely rates of chronometers. BUT it occurs to me that this doesn't mean that practicing navigators all knew that. If they believed they could rate their chronometers by doing a couple of lunars in a row, then they would do them even if they found the results useless.

And indeed, I've noticed a tendency for paired lunars in the whaleship logs I've been charting. After many months without doing any lunars at all, they would do one lunar (one set) and then another lunar a day or two later. So it's just possible that they believed they could rate their chronometers this way. Another possibility (which I think is a little more likely, but I'm not saying I can prove it) is that these paired lunars are evidence of training in progress. The ship's captain or head navigator does a lunar as a demonstration for an apprentice navigator on, say, Monday, and then on Wednesday the apprentice tries one himself (presumably with the master verifying the results). That migt explain these pairs. Any other ideas why there would be paired lunars like this?

Frank E. Reed
[X] Mystic, Connecticut
[ ] Chicago, Illinois

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