The navigational stars

The almanac lists fifty-seven navigational stars, bright and well spread, with their sidereal hour angle and declination; the Moon and four planets join them. At twilight, when the horizon is still sharp and the brightest stars are out, a star finder set to the local hour angle of Aries shows which are up and where. Choose three or more spread around the horizon, at altitudes between about fifteen and seventy degrees: low stars suffer refraction, high ones are hard to bring down to the horizon. Sirius is the brightest star in the sky; Arcturus, Vega and Capella anchor the northern evenings, Canopus and Achernar the southern.

A round of stars taken within a few minutes gives a fix without the running fix's run.

How many navigational stars does the almanac list?
Which altitudes serve a star sight best?

Show the answers
  1. How many navigational stars does the almanac list? Fifty-seven Fifty-seven stars, bright and spread over both hemispheres, with the Moon and four planets beside them.
  2. Which altitudes serve a star sight best? Between about fifteen and seventy degrees Low stars suffer refraction; high ones are hard to bring down to the horizon.

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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