A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David Pike
Date: 2015 Dec 1, 08:09 -0800
Jaap vd Heide you wrote: Isn't the story about "simplification at high latitudes" a matter of proportions? Which will not hold true for let's say Dubhe when you're up near Tromsø?As in: it is true when coLat is small in comparison to coDec, which will basically "squeeze" the navigational triangle. Which in turn is the same reason Azimuth for Polaris will be very close to N (0) no matter what the LHA is.
I think what you’re saying with respect to Polar simplification is similar to the Polaris case, but not quite the same. For a PZX triangle, where P is the Pole, Z is the observer’s Zenith, and X is the position of the astral body, in polar simplification, P and Z are almost coincident, whereas for Polaris simplification P and X are almost coincident. Both turn the PZX triangle into a straight line, but a different side tends towards zero length. Interestingly, things suddenly become a bit meaningless if you were to try and shoot Polaris very close to the N Pole, because P, Z, and X all become almost coincident, and the azimuth of Polaris begins to move significantly with LHA, because colat and codec are both small. DaveP