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G'day Bruce,

> When you used bubble sextants on the water did you use the averaging
> mechanism?

No. They are not worth the effort. The averaging mechanism was designed for
the relatively predictable motions of an aircraft; not the pitching, yawing,
bouncing of a small vessel.


The least motion I have ever seen in a vessel is flat calm
> with 35 thousand tons of iron ore in the holds with a ship with a flat
> bottom. You could almost shoot pool if you had a table.There was some
> motion, but certainly less than you would find in an aircraft.
>
I have heard that you can balance a dime off the taffrail of a supertanker
but the vessels I have attempted bubble sextant observations from were small
and certainly not as stable as a 35,000 tonner! Actually, I would love to
have an opportunity to attempt this one day, to see what it is like. But
even at that, I have been sitting in my own boat in flat calm water with
nary a discernable motion and the bubble still tended to be skittish.

> I like your comet about the celestial navigation in the far north, as my
> father was a bush pilot in Northern Quebec in the 60's. Magnetic compass
> was questionable. It was all floats so you never even got to set the
> gyro to a handy airstrip direction.There was no VOR, and few radio
> stations to pick up on the RDF.  On top of that the land is featureless
> and the ceiling is always low. His joke was if he took the Beaver up
> over 1000 feet he would get a nosebleed since he was so unused to it.  I
> gather the GPS has made things better, but it too suffers in high
> latitudes, although I can find no published facts on this on the web. He
> didn't have an astro-compass on his plane.
> I have a friend who often finds himself in the North as a ship's
> navigator who says the GPS has problems because the satellites get too
> close to the horizon. Even the the Gyros (both mechanical and FOG) get
> wonky too. Fortunately, the sun is always up when he is there.
>

GPS is immensely popular in these parts. Most hunters now have them strapped
to their skidoos. I have used GPS up in Resolute Bay and Ellesmere Island
without any apparent ill effect. That being said, I cannot say that my use
of GPS in these parts has been extensive so I can only comment on my
experiences during my brief interludes up there. In the southern and
mid-Arctic; that is at Latitudes of 60 - 70 degrees, I have found GPS to be
very reliable. Satellite phones are another matter altogether...

I have a couple of astro compasses in my collection. At one time, they were
mandatory on all aircraft flying up here but I am not certain if this is
still the case. Regardless, I seriously doubt if most of these young pilots
would know the difference between Venus and a streetlamp. It is, from what I
have observed, all about button-pushing.

Incidentally, do you have a copy of Kieth Greenaway's "Arctic Air
Navigation"?  If not, you should pick up a copy. Published in 1952, it was
at the time, on the leading edge of air navigation in the polar regions. It
was all astro compass and sextants back then.


Robert



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