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Re: Transcription of Worsley's Log
From: Henry Halboth
Date: 2009 Mar 17, 07:56 -0700

Hi Brad + George,

I have not been able to follow in detail all that has transpired in this matter, however, would be happy to assist or participate in the determination of Worsley's true CE, based on the position of Cape Belsham. I f you would be so kind as to restate for me his position relative to the Cape, whether at or by bearing and distance, as well as his sight particulars, i.e., body, altitude, height of eye, and index error, plus chronometer time of observation and whether or not corrected for assumed error on date of observation, I would be pleased to work up the true CE at the time of observation. This was rather a routine exercise in years gone by - before the advent of the radio time tick and after the demise of lunars.

Regards,

Henry

--- On Mon, 3/16/09, bmorris@tactronics.com <bmorris@tactronics.com> wrote:

From: bmorris@tactronics.com <bmorris@tactronics.com>
Subject: [NavList 7657] Re: Transcription of Worsley's Log
To: NavList@fer3.com
Date: Monday, March 16, 2009, 8:58 PM

Hi George

Now that I have some confidence in the digits and have the spreadsheet, I can
next investigate his chronometer and chronometer error.  On 7May1916, Worsley
indicates that his "chron[ometer] was much slower than I had allowed".
 While we can only estimate his rate, we can certainly investigate his initial
error.

On 24Apr1916, Worsley writes that the longitude of Cape Belsham is his only
opportunity of "rating" his chronometer.  The important criteria in
this calculation are an exact knowledge of his latitude, longitude, the alitutde
of the body and the chronometer reading.

I examined my navigational charts of the Antarctic Penninsula and extracted the
position of Cape Belsham.  The chart number is 29104 (NSN 7642014012241)
"King George Island to Clarence Island" with Elephant Island smack in
the middle of the chart.  Cape Belsham is clearly marked.  I make the latitude
to be South 61 degrees 6 minutes 22 seconds and the longitude to be West 54
degrees 53 minutes 45 seconds.

Next, I used my spreadsheet to enter exact values.  On 24Apr1916, Worsley
writes that his chronometer was slow by 10 minutes 51 seconds and then proceeds
to use 24.40.1 as his chronometer reading.  From this we can expect that his
chronometer actually read 24.29.10 (+10.51 = 24.40.1).  Using 24.29.10; the
equation of time for the day 1 minute 53 seconds and the exact latitude, I can
vary the chronometer error until the precise longitude is obtained.

To obtain the precise longitude, I must use 13 minutes 28 1/2 seconds.  That
is, while Worsley makes his chronometer 11 minutes 55 seconds slow, I am an
ADDITIONAL 2 minutes 33 1/2 seconds slower.  

That is a substantial difference, to say the least.  

Best Regards
Brad

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