NavList:

   

Reply

Brad Morris provides an interesting account of occultations by the Moon,
used by Shackleton in "South".

It's an acceptable and accurate way to check a chronometer, which can be
used even at sea, if a sufficiently bright star happens to be occulted. The
trouble is, that bright stars don't occult very often. So chronometers can
be checked at sea that way only occasionally, and according to Sod's law,
those occasions would hardly ever be when they were really needed.

Shackleton had the advantage (though I doubt if he saw it as an advantage)
of having his ship stuck in ice, so a telescope on a tripod stand could be
used, which enabled his astronomer (James) to see stars down to 5th
magnitude with some ease, especially in the clear Antarctic air. That
enabled him to see frequent occultations, timing four on one day, on 24 June
1915. At that time, the Moon was very nearly full, with just a sliver of
darkness where it met the star, so the observations, of 5th mag stars, must
have been  rather tricky ones, which would have been difficult or perhaps
impossible to made from a ship afloat.

Shackleton himself was a supremely competent explorer, who always seemed to
do the right thing. However, his big mistake was pushing Endurance so firmly
into the ice in the first place.

George.

contact George Huxtable, at  george@hux.me.uk
or at +44 1865 820222 (from UK, 01865 820222)
or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.


--~--~---------~--~----~------------~-------~--~----~
Navigation List archive: www.fer3.com/arc
To post, email NavList@fer3.com
To , email NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---

   

Reply