Celestial navigation practices


Mar 22, 2003
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Charts should have plenty of bearing lines defined by two visual points, that may be either landmarks or tangents.
After the Hawke collided with Olympic in the Solent back in 1911, Hawke's Lt. Aylen took a fix with reference to bearings that were taken off four specific landmarks. The magnetic bearing lines of the fix (shown in red below) were: S88W [252°T] to Egypt Point, S34W [198°T] to the east bank of the River Medina, S31E [133°T] tangent to the east shoreline of the Isle of Wight, and S10E [154°T] to the bathing house on Old Castle Point.That was not the point of collision but rather the point where Hawke came to a stop following the collision. The most likely point of collision would have been about 100 yards bearing about SE true from Aylen’s fix position.
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Doug Criner

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The bearing lines on charts that I am familiar with are true bearings. Many ships today (but of course, not in 1911) use a gyrocompass, but if a sailor is using a magnetic compass, then he needs to correct to true or vice versa.
 
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Mar 22, 2003
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Hi Doug, your absolutely correct.
The reported magnetic bearings such as S88W to Egypt Point were as given by Lt. Aylen in evidence. The true bearings, after correcting for magnetic variation (which was was almost 16°W in that region on that date) was therefore 255° True as indicated in brackets. This 16° correction, which was obtained from a channel pilot publication after correcting for annual change in variation, was applied to all four magnetic bearings given in evidence, and those lines were then drawn on the chart which resulted in the crossing point shown. It was great fun to do when Mark Chirnside and I wrote our book.
 
Mar 22, 2003
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By the way, anyone interested in that 1911 collision between Hawke and Olympic, you can pick up a copy here:
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Scott Mills

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You know now that I think of it, we haven't really had a dedicated thread for navigational art and practice in 1912, so I figured this would be a good place to start. But now is also the time for me to reveal the depths of my ignorance regarding such an arcane and interesting topic -- this is a subject on which I have only dared look into very recently so pardon if I come across as an absolute buffoon talking out of the wrong end of the GI tract.

So far from what I've read of the inquiry transcripts I can only find passing references to taking star sights for latitude and longitude from 4th Officer Boxhall's testimony. Many articles written by members more experienced than myself also mention the noon sight for latitude -- Dave Gittins in particular has an article somewhere here detailing the various navigational techniques expected of different levels of certification.

One question I have regarding the noon sight is whether the chronometer was used for the calculation of latitude? I know the method of latitude by noon sight involves the use of solar declination tabulated in the Nautical Almanac but I'm not sure if the chronometer was a must for this technique in those days.
Celestial navigation! Psh. They should have just used their GPS. ;)
 

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