Sunset times

[Frank Evans]

If it is of any help, the Nautical Almanac gives the following
explanation of its basis for the tabulation of sunrise and sunset times:
At sunrise and sunset 16 minutes (angle) is allowed for semidiameter and
34 minutes (angle) for horizontal refraction so that at the times given
the sun's upper limb is on the visible horizon; all times refer to
phenomena as seen from sea level with a clear horizon.
-- 
Frank Evans