A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David Iwancio
Date: 2020 Jan 4, 12:51 -0800
A possible trip-up is forgetting that a minute of longitude is 1 nautical mile only on the equator. At my own latitude of around 39°, multiplying 0.225' by my latitude's cosine would give me an error of 0.17 nmi.
Also, unlike parallax and aberration, the effect this would have on your sight depends heavily on the azimuth of the body you're shooting. If I were to shoot a body with an azimuth 045° at my latitude, my line of position would be off by 0.12 nmi (0.17 multiplied by the cosine of the azimuth).
As a footnote, I think it's been a long time since DUT1 has been allowed to reach 0.9 s, if ever. The folks in charge of determining leap seconds, IERS, seem to start getting anxious around the 0.5 s mark. I think the double-tick coding on WWV and CHU can only handle a maximum DUT1 of 0.8 s.