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    Titanic's last stars
    From: Paul Hirose
    Date: 2012 Mar 15, 17:05 -0700

    With the 100th anniversary approaching, I wonder if has anyone has
    a theory on what stars Mr. Lightoller shot to give Titanic her last fix.
    Almost two years ago I began looking into the question, but got busy
    with other things and never finished. One sticking point I remember was
    uncertainty of the time offset between the ship's clocks and Greenwich.
    
    For what it's worth, I present my old notes. These merely quote
    testimony from the US and UK inquiries, except for the last two
    paragraphs where I came up with some hypotheses. View them with
    suspicion. They're just some preliminary thoughts on the position at the
    observation time.
    
    I can't remember whether or not my search for material of navigational
    significance included all the testimony or just part of it.
    
    The testimony from both inquiries is online:
    http://www.titanicinquiry.org/
    
    Also see Encyclopedia Titanica:
    http://www.encyclopedia-titanica.org/
    
    One article at that site offers a theory on why the position transmitted
    by Titanic was so far off: a 1 minute blunder in determining the error
    of the deck watch with respect to the chronometer.
    
    http://www.encyclopedia-titanica.org/its-a-cqd-old-man-4146-north-5014-west.html
    
    There may be something in his theory. However, I'm skeptical that lines
    of position from the star shots would be advanced to a common time, as
    stated by the author. Although I suspect the idea was in print by 1912,
    it seems too newfangled to be the practice aboard Titanic. What do you
    think?
    
    
    Here are my notes of two years ago:
    
    "When you take stars you always endeavor, as they did that night, to
    take a set of stars. One position checks another. You take two stars for
    latitude, and two for longitude, one star north and one star south,
    one star east and one star west. If you find a big difference between
    eastern and western stars, you know there is a mistake somewhere. If
    there is a difference between these two latitude stars you know there is
    a mistake somewhere. But, as it happened, I think I worked out three
    stars for latitude and I think I worked out three stars for longitude."
    Boxhall, US day 10.
    
    "Capt. Rostron said it was a very, very good position. After I had
    worked these observations of Mr. Lightoller's I was taking star bearings
    for compass error for myself, and was working those out. That is what
    kept me in the chart room most of the time. I was making computations
    most of the time." Boxhall, U.S. 10
    
    "At 11.46 p.m., ship's time, it was 10.13 Washington time, or New York
    time." Boxhall, US day 10.
    
    "My duties comprised working out celestial observations, finding the
    deviation of the compass..." Pitman, U.S. day 4.
    
    "I was on the bridge from 6 to 8 o'clock p. m... No; I could not say
    that, sir, because I was inside, working out observations." Pitman, U.S.
    day 4.
    
    "Yes; we took stellar observations and also observations for compass
    deviation... No, sir; I did not take the stellar observations myself. I
    took the time for them, and Mr. Lightoller himself took the
    observations of the body... We just took a set of them at sunset, or
    just as it was getting dusk, when the stars were visible. It was about
    6 or 8 o'clock that we took them... After that I started working out
    the observations... in the chart room; in the chart house... I was
    there alone until 8 o'clock... I did not finish them. Mr. Boxhall took
    on then and finished  them." Pitman, U.S. day 4.
    
    "They [ship's clocks] are set at midnight every night... They are
    corrected in the forenoon, perhaps half a minute or a minute; that is
    all... The clocks are set at midnight, but that is for the approximate
    noon position of the following day. Therefore Sunday noon the clocks
    will be accurate." Pitman, U.S. day 4.
    
    "I can give you the Greenwich time... 5.47 - 2.20 - 5.47 Greenwich mean
    time: 2.20 apparent time of ship." Lightoller, during Pitman's
    testimony,  U.S. day 4.
    
    "I can not remember. If I had a chart here I could tell you in a minute.
    South 84 or 86 west would be the true course we were making after
    5.50; south 84 or 86, I am not quite certain which, was the true
    course." Pitman, U.S. day 4.
    
    "Captain, we were given the ship's time and the Greenwich time. Are you
    able to give the New York time, as to when this vessel sank?" [Sen.
    Smith] "Take five hours from the British time." Pitman, U.S. day 4.
    
    "You see, on these ships each operator has a clock for the purpose of
    keeping New York time and Greenwich time on the way across." (Bride,
    U.S. day 10)
    
    "We had two clocks, sir... Yes, sir; one was keeping New York time and
    the other was keeping ship's time... There was about 2 hours difference
    between the two."
    
    "We are there to do the navigating part so the senior officer can be and
    shall be in full charge of the bridge and have nothing to worry his
    head about. We have all that, the junior officers; there are four of
    us. The three seniors are in absolute charge of the boat. They have
    nothing to worry themselves about. They simply have to walk backward
    and forward and look after the ship, and we do all the figuring and all
    that sort of thing in our chart room." (5th ofc Lowe, U.S. day 5)
    
    "We worked out the positions, sir; yes, sir... No, sir; we do not use a
    chart. If we wish to place the position on a chart so that we may know
    the locality we may do so, because we have charts there... But we work
    them out by tables and other things - books." (5th ofc Lowe, U.S. day 5)
    
    "From 6 to 8 I was busy working out this slip table as I told you
    before, and doing various odds and ends and working a dead-reckoning
    position for 8 o'clock p. m. to hand in to the captain, or the
    commander of the ship."(5th ofc Lowe, U.S. day 5)
    
    "Her speed from noon until we turned the corner was just a fraction
    under 21 knots... I used the speed for the position at 8 o'clock, and
    got it by dividing the distance from noon to the corner by the time
    that had elapsed  from noon until the time we were at time corner." (5th
    ofc Lowe, U.S. day 5)
    
    "We have the log every two hours, and we are all the time navigating. We
    do not take observations once a day. We perhaps take 25 or 30
    observations a day."
    
    "I know from calculations made afterwards that we were making S. 86 true
    [when he came on watch at 1800]." (Lightoller, British inq., day 11,
    Q.  13498)
    
    "How often when you are on watch do you mark the position of the ship on
    the chart?" "Only at noon." (Pitman, UK, day 13, Q. 15223)
    
    "15639. So that what you had to do after the disaster had occurred would
    be to take the position on the chart at 7.30, take your course, take
    your speed and calculate where you would be?"
    "Yes, from the 7.30 position I allowed a course and distance which gave
    the position. I worked it out for 11.46 as a matter of fact."
    (Boxhall, UK day 13)
    
    "15643. Can you tell me what speed you assumed as between the 7.30
    position and the time you struck?"
    "Twenty-two knots." (Boxhall, UK day 13)
    
    "15646. Was it an estimate you formed on any materials as to revolutions
    or as to the patent log?"
    "No, I never depend on the patent log at all. It was an estimate that I
    had arrived at from the revolutions, although I had had no revolutions
    that watch; but, taking into consideration that it was smooth water
    and that there ought to have been a minimum of slip, I allowed 22
    knots."  (Boxhall, UK day 13)
    
    "15664. You saw that in the order book?"
    "Yes, I saw it and I remarked to the Chief Officer between 4 o'clock and
    6 o'clock that I considered the course ought to have been altered some
    considerable time before 5.50 - that is, if it was meant to be altered
    at the corner, 42 N., 47 W. Whether we spoke to the Captain about it or
    not I do not know. I just remarked that to the Chief Officer, and the
    course was altered at 5.50. I consider that the ship was away to the
    southward and to the westward of that 42 N. 47 W. position when the
    course was altered. (Boxhall, UK day 13)
    
    "15676. Then for the purpose of working out what your position was when
    the collision occurred did you actually have recourse to the chart?"
    "None whatever. I had the 7.30 position in my work book."
    "15678. You would not have to return to look at the chart after the
    accident?"
    "No, I had used that same position two or three times after giving it to
    the Captain, and that same course I used two or three times after
    giving it to the Captain as well, between 10 o'clock and the time of
    the collision, for the purpose of working up stellar deviations."
    (Boxhall, UK  day 13)
    
    "16955. (The Solicitor-General.) It is not wind, your Lordship sees. (To
    the witness.) Whether there is a wind or no wind, the current will flow?"
    "Yes, but invariably we find a strong easterly set there; very often we
    find that the Gulf stream -" (Boxhall, UK day 13)
    
    
    Ship time was 3:27 behind Greenwich, based on Boxhall's statement: "At
    11.46 p.m., ship's time, it was 10.13 Washington time, or New York
    time."  So it was 27:13 at Greenwich, and 27:13 - 23:46 = 3:27. This is
    confirmed  by Lightoller: "I can give you the Greenwich time... 5.47 -
    2.20 - 5.47  Greenwich mean time: 2.20 apparent time of ship."
    
    Boxhall obtained the 2346 DR position N41 46 W050 14 from Lightoller's
    1930 stars, assuming 22 knots and true course 266. This is so close to
    due  west that we may as well use mid-latitude sailing. Elapsed time =
    2346 - 1930 = 4:16 = 4.27 hours. Multiplied by 22 knots gives 94 miles.
    Plot that distance on course 086 true from the DR position. Northing =
    6.6 NM, mid-lat = N41 49 = 41.82, easting = 93.6 NM, lon. diff = 126' =
    2 06. Consequently the 1930 (2257Z) celestial fix was N41 53 W48 08. The
    Sun altitude would have been -12 degrees at that time and position.
    
    --
    I filter out messages with attachments or HTML.
    
    
    
    
    

       
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