Latitude by Polaris

Polaris stands within about three quarters of a degree of the celestial pole, and the altitude of the pole equals the observer's latitude. Take its altitude at twilight, correct it to the observed altitude, then apply the Polaris corrections from the almanac's own table, entered with the local hour angle of Aries and, for the small second and third terms, the latitude and the month; the result is your latitude. In the southern hemisphere there is no such star: the noon sight and the sight reduction serve.

It is the oldest sight there is, and still the simplest check on a dead-reckoning latitude on a clear northern night.

Why is the altitude of Polaris not exactly the latitude?
The Polaris table is entered first with what?

Show the answers
  1. Why is the altitude of Polaris not exactly the latitude? It lies about three quarters of a degree from the pole and circles it The almanac's Polaris table corrects for its small circle around the pole.
  2. The Polaris table is entered first with what? The local hour angle of Aries The star's place on its circle depends on the hour angle of Aries at the moment of the sight.

The twelve evenings

  1. The celestial sphere
  2. The sextant
  3. Time and the almanac
  4. Correcting the altitude
  5. The noon sight
  6. Latitude by Polaris
  7. The navigational stars
  8. The intercept method
  9. Plotting the position line
  10. The running fix
  11. The Moon and the planets
  12. The day's work

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