NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Frank Reed
Date: 2026 Feb 9, 07:28 -0800
We are coming up on "Sun Slow Day" on Tuesday. Because of this, the Sun's GHA at any fixed UT barely changes all week. So you can get the Sun's GHA at any UT/GMT from a simple computation from Feb 8 - Feb 14, accurate to less than a minute of arc error:
GHAsun = 176.46° + (15×h + m/4 + s/240),
where h,m,s are (of course!) hours, minutes, seconds of the UT time. That number out front, 176.46, is the GHA of the Sun at Greenwich midnight. It barely changes, and that's why the computation is simple this week. Naturally if the result if greater than 360, you bring it back in range by subtracting 360.
This "simple computation" is good for Valentine's Day, but don't try this at Christmas! (the week around December 25 has the most rapid changes in the initial value of the GHA at Greenwich midnight during the year).
Frank Reed
Conanicut Island USA
Advanced Celestial Feb 14-15: ReedNavigation.com/adv-class/
