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    Sunrise - the Positive Side
    From: William Hawes
    Date: 2013 May 3, 17:45 -0700


    Observation of the sun at sunrise seem to be getting a bit of a bad wrap on the NavList these days. I must come clean and admit that I am a keen advocate of observing the sun at sunrise and have made many dozens of such observations during my time with the Royal Navy and Royal Canadian Navy as a submarine navigator. Before anyone fires back a nastygram, let me hasten to add that I never actually obtained or tried to obtain an LOP from a sunrise observation. In fact the sextant was back in its box by the time I made the sunrise observation. What I used at sunrise to observe the sun was not a sextant, but rather the Azimuth Circle on the Pelorus bridge gyro repeater. By using the Azimuth Circle prism to observe the bearing of the sun at the true time (not the visible time) of sunrise and compare it with the calculated bearing, one is able to determine the gyro error. A very useful bit of navigation information. Knowing the gyro error allows one to adjust planned tracks for this error and thus maintain a better DR position. Of course any bearings subsequently obtained from the gyro would also be adjusted for the error as well. We tried to check the gyro error at least twice a day at sunrise and sunset and also at times of opportunity such as when on a transit. It was reassuring and a sound navigation technique to use the bearing of the sun to confirm the correct operationm of the gyroscope. There was a satisfaction in knowing that navigation was somewhat safer once the gyro error had been determined - especially if it was a 1/2 degree or less (about the best that could be hoped for back in those days with the vagueries of magslip and synchro bearing re-transmission from the master gyro to the repeat).

    An added bonus of these sunrise and sunset observations was that I occasionally got to see the Green Flash. Unfortunately I never saw it as often as I would have liked. Although I was always looking intensly for it, I probably didn't observe the Green Flash more than about 6 or 7 times in my entire time at sea. In fact, to the best of my recollection, I think I only ever observed the Green Flash at sunrise, not at sunset.

    Just my thoughts on happy memories of sunrise (and sunset) observations.

    wmh
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