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    Re: Transcription of Worsley's Log
    From: Brad Morris
    Date: 2009 Mar 25, 09:22 -0400

    Hi Henry

     

    There is something that occurred to me. 

     

    Let us first establish that Worsley is a competent navigator.  He obviously knows how to determine his chronometer error.  The calculation in his logbook matches the methodology proscribed for this situation.

     

    Secondly, neither George nor myself can establish with absolute certainty where he took his observation.  Point Wild is an assumption.  It makes logical sense, as, from their own accounts, it was very difficult to move over land in the Antarctic.  Point Wild was the location of the camp.  Most likely the observation was there but agreed, we can’t prove it.

     

    Thirdly, as to the chronometer rate, it is a player only after the journey begins, not for that instantaneous determination of chronometer error.

     

    Here is what has occurred to me.  When Worsley wanted to know his DLo to Cape Belsham, he first had to determine WHICH point was Cape Belsham.  It is not like there was a big sign over it, with an arrow saying “Cape Belsham Here”.   I have found a map from 1912, a German Stieler map, of the Antarctic Peninsula.  I attach it herein.  While I make no pretense about this being the one that Worsley used, it does offer a suggestion.  Elephant Island was not a highly explored location.  Suppose for a moment, that the prominent Cape that Worsley selected was the one just to the south of Buskin Rocks on the later chart.  That IS about 16 arc minutes away!   If we accept this theory, then all the reductions and chronometer error determinations make sense.

     

    We all look at the modern charts and say, that’s Cape Belsham.  Its labeled.  Worsley looked at a pile of rocks under great adversity and (MAYBE) said, Cape Belsham is that large prominent point down the coast, not this pile of little pile rocks.

     

    Best Regards

    Brad

     

     

    From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of hch
    Sent: Tuesday, March 24, 2009 4:40 PM
    To: NavList@fer3.com
    Subject: [NavList 7755] Re: Transcription of Worsley's Log

     

    Hi Brad,

     

    Perhaps we are working at cross purposes here, or misunderstand each other. I am not trying to correct Worsley's work, but rather have sought to simply explain the working of his sight for Longitude and his methodology of calculating his CE therefrom, and thereby to demonstrate to the List in general how this was done historically.

     

     It was my understanding that both you and George were not factually aware of the actual position from which his observation was made and that the selection of Point Wild was an assumption, calculated or otherwise - if I am wrong then of course Worsley appears to have made a mistake or we misunderstand the true meaning of his 1 min + 4 sec. DLo.

     

    I have simply played the part of the devil's advocate in, without his confirmation of the observation site, considering him to have been too good a navigator to have misstated the DLo between that site and his knowledge of the position of Cape Belsham. I have tried to express the opinion, perhaps clumsily, to the effect that, without a factual knowledge of his observation site position and his knowledge of the position of Cape Belsham at the time, we are unable to assess the accuracy of his work in the context of 1916. This in no way seeks to express an opinion with respect to the "what if" as respects the now known position of Cape Belsham and Point Wild or how this may have affected his subsequent movements.

     

    Perhaps time was of the essence, however, in like circumstances it perhaps may have been more appropriate to have waited a sufficient time to have confirmed the CE and position by additional observations over a longer period of time.

     

    Regards,

     

    Henry

     

     

     

    - On Tue, 3/24/09, bmorris{at}tactronics.com <bmorris{at}tactronics.com> wrote:


    From: bmorris{at}tactronics.com <bmorris{at}tactronics.com>
    Subject: [NavList 7748] Re: Transcription of Worsley's Log
    To: NavList@fer3.com
    Date: Tuesday, March 24, 2009, 1:26 AM


    Hi Henry

    After a tremendous amount of typing, I finally saw what you were saying and started over.  We agree, Worsley saw his longitude as West 54-50-00 and we think, based on modern charts, that the longitude is West 54-53-45.  This gives us a delta longitude of 00-03-45. 

    So why does my 2.13 not agree with your 1.804?  I used a great circle distance, accounting for the difference in latitude as well as the distance in longitude.  Your calculation, I believe, accounts only for the DLO.  Fundamentally, these values are fairly close and not truly worthy of extended discusion. 

    ----------------
    This is the point I am trying to drive at, however.  If his observation and consequent reduction yields West 54-19-45 and he "knows" West 54-50-00, then his DLO is 00-30-15 (arc).  If we convert this arc to time, we should get 2 minutes 1 second of CE, not 1 minute 4 seconds. This is where I would like a bit of help in my understanding.

    I think from your equations of the other day that {you think} he estimates his distance to Cape Belsham at 1 minute 4 seconds (time) and therefore he must subtract that out from his CE.  That supposes that there are 16 minutes of arc to Cape Belsham from Point Wild.  That is very high of the mark.  He can see it from Point Wild pretty clearly.  I measure it on my chart 29104 at 00-01-30 arc. So 1 minute 4 seconds time should really be much lower, or roughly 6 seconds time. 

    Thats a 58 second delta.  If you read Worsley's note on 7 May 1916, he states that he is "about" 20 miles astern due to his CE, on an easterly course.  So even Worsley knows his chronometer is slower than he expected.

    This can be attributed to (1) Worsley doesn't have a good idea of the rate of his chronometer.  (2) Worsley doesn't get the right value for CE on Elephant Island.

    Which one?  I simply don't know.  I find both outcomes strange.  He should know the rate of his chronometer after working with it on this expedition.  Maybe he just started working with this pocket chronometer after abandoning all others on the ice.  He also knows the longitude of Cape Belsham fairly well (not to modern values, but not too far off). 


    -------------------------------------------
    Your calculation was

        Meridian angle    02-55-24.6 East (in time)
                                    11-59-60
        LAT            09-04-35.4
        GAT            12-41-54                    Longitude        03-37-18.6 W (time) = 54-19-39 W (arc)
        DLo Cp Belsham        00-01-04.0 W (time) = 00-16-00 W (arc)
        Calc Lo Cp Belsham  03-38-22.6 W (time) = 54-35-39 W (arc)
        True Lo Cp Belsham  03-39-32.2 W (time) = 54-53-02 W (arc)
        Diff = CE, Slow     00-01-09.6 (time)   = 00-17-23 (arc)

    The "Dlo Cp Belsham" is too large.  It should read 00-00-06 W(time)=00-01-30 W (arc).

    Another very minor point, the "True Lo Cp Belsham" should read 54-50-00, not 54-53-02 (thats the modern value).  This would reduce the time downwards from 00-01-09.6.

    ---------------------

    I do appreciate your time on these points Henry.  It is helping me to get this right!

    Best Regards
    Brad Morris





     



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