A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Tony Oz
Date: 2017 Jun 15, 05:00 -0700
I've got a 24-hour mechanical watch to keep UTC for my observations.
To get the local time I move the outer (rotatable) scale's "3" mark to coincide with the mail scale's "24" mark, because our time zone is UTC+3.
Today is the sunny day at Saint-Petersburg (60°N 30°E) so I decided to try using my watch as a solar compass. I expected to get N/S direction aligned with outer scale's "12"/"24" marks. I used a match to cast a shadow along the hour-hand, but the resulting direction was way off...
I re-checked the scales alignment, the correctness of the UTC my watch show - all was OK.
Only few minutes later I got it: I must use not the zonal time but my apparent local time for the scale setting.
So, being at 60°N 30°E, which by coincidence is the middle of the UTC+2 strip, I must align the outer "2" with the main "24".
After correcting this I got reasonable N/S direction. This is a good lesson (for me) to always remember my longitude rather than the time zone. If I were off the 30°E meridian - I should have rotated the outer scale accordingly - to coincide with local apparent time.
Hope that helps someone too. :)