Originally Posted By: hikermor
Originally Posted By: Russ


A bit of celestial knowledge can be a god-send.


Yes indeed! In the case I mentioned, we had started before dawn on an ascent of Orizaba, the tallest of the Mexican volcanoes. My companion was navigating with his compass. It was a beautiful night and I had Polaris in sight,so we got straight quickly. The considerable variation was probbly due to iron in the surrounding lava flows.

Give me a starry night any day....

Get a free planetarium app for your smartphone. Given it has a recent GPS fix (or you can tell and input your location coordinates within a 100 miles error spot) you can figure the magnetic declination measuring the azimuth of any visible celestial body with your compass (e.g. Sun, Moon, any bright star poking through the clouds). All of them are capable of showing the true azimuth of any celestial body in real time, just subtract the two.