Course / Latitude from the noon Sun

Part II · First sights · Page 3 of 3

Working a noon sight

  1. Note the time of the highest altitude and convert it to UT.
  2. Correct Hs to Ho.
  3. Find the Sun's declination for that UT.
  4. Zenith distance z = 90° − Ho. It takes the name opposite to the Sun's bearing: Sun bearing south, z is north.
  5. Latitude = declination + z, each with its name. Same names add; contrary names subtract.

Off Hawaii, January 14, 2026, highest altitude at 22h36m00s UT, Sun bearing south, Ho 48°47.9'.

Dec S 21°10.3'; z = 90° − 48°47.9' = 41°12.1' N

L = S 21°10.3' + 41°12.1' N = N 20°01.8'

At noon the Sun's GHA equals your west longitude, so the time of noon gives longitude too. But the top of the curve is flat, so that longitude is only approximate.