NavList:

We are supposed to shoot azimuths once every watch, but usually it happens two or three times a day.  We need to track and check the error of our gyro compass as well as double checking the deviation table on the standard compass.   It is, in fact, the only real celestial navigation done on commercial ships at sea on a regular basis.  There is a log book kept for this.

 

Tos shoot azimuths, we put either an azimuth circle or alidade on a gyro repeater and take the sight of a celestial body.  The most common body is the sun; but stars, the moon, and planets can all be used.  I find Alidades the most accurate due to the magnification of the scope and the hair sight in the optic.  The trick is to keep the repeater level during the observation and there is a bubble to help do this.  For alidade sights, I can reasonably shoot to the nearest 0.25 degree with any body , and with the azimuth circle (especially of the sun) to the nearest 0.5 degree.  The biggest problem is that the repeaters only display whole degrees, so you are eye-ball interpolating between the hash marks.

 

Jeremy

 

Jeremy,

I'm curious whether you could give us some additional details (e.g. "why" and "how") about these shots of azimuths.  Thanks.


Peter Hakel

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I actually have little faith in Polaris.  The star is dim and the horizon is rarely good when I observe it.  I tend to get better results from 1st order stars which I observe with the best possible horizon available.  The only real advantage these days is that it is easy to reduce by table.  It is also a favorite of the second mates to shoot azimuths.

 

Jeremy

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