RE: [Paddlewise] Longitude and astronomy

PeterO wrote
........The clock would then only have to remain within spec for 24 hours
and measure and not for months or years to maintain synchronism with
Greenwich. Presumably there were enough stars visible in both the southern
and northern hemispheres so that Cook in Australia could use the tables
developed at Greenwich to try out the lunar method...........

Robert wrote
.......Not really. The only useful clock is a VERY accurate one. You cannot
stay linked with Greenwich by using an inaccurate clock and "correcting" it
for local time. For one thing, when you are actually moving east west, local
time "noon to noon" is no longer exactly 24 hours. In fact, it is the
discrepancy that you are trying to detect to  see how far east west you have
gone...............

G'Day

Robert I was trying to explain that there is no need at all to use a clock
to stay linked to Greenwich or any other longitudinal reference point when
navigating by the stars, moons and planets. The lunar method implies this.
The navigator would need a record or memory of their relative locations at
particular days of the year and times of the night. Days of the year and
times of the night can be measured in many ways without the need for
sophisticated manufacturing and star maps were a commonplace. Some articles
describing the techniques of Polynesian navigation.

http://www.penn.museum/sites/navigation/intro.html

http://www.teara.govt.nz/en/canoe-navigation/2

All the best, PeterO
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