NavList:

 

Although the Sun amplitude table lost its main reason for existence in the
19th century, conservative maritime traditions keep it in being, and, no
doubt, retain it as an examination topic.

George is correct here!  I have had an amplitude on 2 of my 3 exams.  I will add that when using calculators, it is faster to punch in the fairly short Amplitude formula then the more lengthy Azimuth equation and therefore the sight is faster to reduce, but this is moot once computers come into play.  If you are using purely tabular methods, the double interpolation of the Amplitude table is faster then the triple interpolation of say HO 229.  I know there are other tables for Azimuth calculation, but I have never used them so can't comment on those.

 

At sea these days, the mates will shoot up to six azimuths a day (one per watch).  Looking in our compass correction book, I see that I'm the only one who's tried an amplitude in a number of years.  All daylight sights are of the Sun, while Polaris is the favorite at night.  When the ship was in the southern hemisphere at night, one of the bright stars was the favorite.

 

On a related topic, I wonder how often a yacht needs to correct its compass?  On a ship we are using the electro-mechanical gyrocompass that is prone to getting a bit off kilter for a number of reasons, and therefore we keep a record on its error.  I would think that the deviation, once determined, would be fairly constant on a yacht as long as nothing metallic is moved around.  Am I correct in this?  I would think that swinging the boat on a range would be the best way to create a deviation table.  Of course in areas of "local magnetic anomalies" you might use a static deviation table and try to determine local variation for future reference, but that is probably fairly rare.

 

Jeremy

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