[4] From the declination of the sun corrected for variation and from the known latitude, the meridian zenith distance is calculated.
From the Greenwich time, the longitude, and the equation of time, the hour angle is obtained.
Now, if H be the hour angle, D the reduced declination, and M the meridian zenith distance, the sun’s altitude may be calculated by the formula—
log versin H + L cos lat. + L cos D-20 = log n,
where n is a natural number, and
n + vers M = covers alt.
Again, to find the azimuth—
vers sup. (lat. + alt.)-vers polar dist. = m,
where m is another natural number, and
log m + L sec. lat. + L sec. alt.-20 = log vers azim.,