NavList:

Bob,

As earlier indicated, you will find the results of my study in the enclosed document.

As far as I am concerned, retrieving the "correct" intercepts has been kind of a headache since it all boils down to understanding the Author's own definition of both "Observed Altitudes" and "Sextant Altitudes".

Both terms actually have the exact same meaning here: they pertain to the Sextant raw altitudes, i.e. not corrected for Instrument errors.

It is a bit unfortunate that - like all too often - altitudes are not clearly tagged, especially to foreign readers.

Whatever ...

As an end result, your own intercepts should now be extremely close from the ones I have derived here and which are reasonably close from the published ones. One reason for the differences - quite insignificant actually - comes from the fact that I did not approximate anything.

Given all the uncertainties of the method - with more than 2 hours between extreme observations here - the difference between clock correction determinations - amounting to about 37 seconds of elapsed time - can hardly be regarded as significant either.

It is nonetheless a "clever shortcut" to "brute-force lunars" to who-ever cannot solve them [through computer software].

Although crystal clear in its principle, this Chichester-Bennet method does nonetheless certainly require a lot of meticulous care in real world conditions onboard a small sailboat.

I think only its third computation can bring sufficient confidence to the Navigator, i.e. the last one implying a Moon intercept actually checked as [extremely close to] zero.

If this can float your boat ...

if not, then revert, including privately if you prefer.

Kermit

antoine.m.couette@club-internet.fr

PS: To you Dave, thanks for pointing us towards an additional reference to this Chichester-Bennett method. The Navigator's Newsletter is a gold-mine !