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    Re: submarine navigation
    From: Jan van Puffelen
    Date: 1996 Sep 12, 14:26 EDT

    At 07:06 12-09-96 -0700, you wrote:
    >I have been doing some reading about submarines in World War II. I was
    >wondering if anyone knows how they handled celistial navigation. If, as
    >stated they ran submerged during the day, could they get a sun fix from
    >underwater? It seems that the periscope, begin so low in the water would be
    >hard to get a good view of the horizon and the sun. Second, is it possible
    >to get a star shot without it begin twlight? As you know, there is only a
    >small window of time (depending on your lat) when you can see the horizon.
    >
    >I wonder if the moon, when it is low would alluminate the horizon enough to
    >get a shot with a star or the moon itself, but begin so low, would you get
    >distortion?
    >
    As a small boy I once came across a German WWII gyroscopic submarine
    sextant. The gyro was brought up to speed by compressed air (which is in
    abundant supply on a submarine). The artificial horizon was provided by the
    gyro and lighted by a small electric lightbulb for the use at night. German
    subs used to surface at night to recharge their batteries when there was no
    horizon visible and used to establish their position by a three star sight.
    As a boy I could not afford this instrument.
    Later, I came across a similar instrument in the Amsterdam Maritime Museum.
    The gyroscopic sextant is not an invention of the Germans in WWII, not even
    of the 20th century. The same museum has a nice brass gyroscopic sextant of
    the early 19th century, designed by one french admiral Fleurieu. There are
    some differences though. The German version is more compact and has the gyro
    built in. The gyro of Fleurieu was detachable and brought up to speed in a
    separate mechanical crank box. And, the articial horizon was lighted by a
    small oil lamp for use at night. But the principle remains the same.
    Both sextants are not on exhibit unfortunately. The collection of the museum
    is many times greater than they can exhibit (even though it is housed in a
    very large building). The curator explained that Dutch exhibits have
    priority (it is after all a Dutch museum) and these foreign instruments are
    only exhibited for special theme exhibitions. At the time I studied in the
    (very extensive) library at 18th and 19th century navigation methods (Lunar
    Distance etc).
    What was done during the day I don't know.
    Regards,
    Jan van Puffelen <puffelej{at}XXX.XXX>
    52d 24'5N 4d 55'E
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