A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David C
Date: 2020 Sep 22, 15:56 -0700
One second earlier or later finds the azimuth nearly due east or due west.
The weather forecast of a week ago was 100% correct - rain and drizzle and strong winds. The equinoctial gales? I woke up at 2am and thought about getting my phone and doing a screen grab of the sun app but decided not to. I did the screen grab in daylight and the dec was -0.1°.
Now to more serious things - your comment had me puzzled. How can the azimuth jump to due east or west in a millisecond? I am guessing that it is something to do with a discontinuity when the lat =0°. I have attached the relevant page from Davis. Note thatat lat=0, dec =0 lha=0 the azimuth field is empty. Note also that as the LHA slowly changes the jump to east or west only occurs when dec = lat. This is confirmed by looking at the pages for lat=1° and the jump to east or wst occurs when dec=1°.
Does this mean that marriners sailing along the equator should avoid a compass check on the equinox?