Mxsmanic wrote:
Walt writes:

Nowadays my relationship with stars centers around my 12" Dob, but
every evening I still look up at the sky and think, "okay, which three
stars will give me the best fix".

And you actually did this in aircraft? I thought aircraft moved too
much for this sort of thing. Don't you have to sight them through a
sextant or similar instrument? Doesn't it bounce around a lot?

I've never learned astral navigation but I think it would be
interesting, even if it might not be practical very often these days.
I've always been fascinated by the SR-71 ANS, which would find and
lock onto stars even in broad daylight from the ground.

--
Transpose mxsmanic and gmail to reach me by e-mail.

Yes, in a KC-135 going 450 knots. Each shot would take one minute; the
sextant had a built-in height averager. An assumed position was
calculated for each shot.

We used a bubble sextant, since a typical nautical sextant, which uses
an artificial horizon, wouldn't work very well; even if you could see
the horizon there would be an error since you were typically 6-7 miles
above the earth's surface.

Conversely, a bubble sextant wouldn't work very well on a boat because
of acceleration/deceleration errors induced by riding up and down
waves. Or so I've been told. I've never taken a celestial shot on a
boat, although I thought about doing it once when sailing my Hobie Cat
on Boulder Reservoir in Colorado. Wasn't much point though. I could see
Longs Peak so I knew where I was. :)

Each star shot would create a Line Of Position. A three-star shot
would, ideally, create a small triangle, and you knew you were
somewhere in that triangle. With any luck your DR (dead reckoning)
position calculated from your last known position 30 minutes before
would be in the triangle. If not, that's when navigation quits being a
science and becomes more of an art.

Of course, we had other state-of-the-art tools, such as pressure
pattern navigation, but I think I explained that in a previous post.
:)

--Walt