Part IV · The fix · Page 1 of 3
Planets: the wandering stars
Venus, Mars, Jupiter and Saturn look like bright stars, but they wander along the Sun's path through the stars, so the almanac lists them hour by hour like the Sun. At twilight they are often the brightest things in the sky, and they reduce just like the Sun with Pub. 249.
- UT
- 23:00
- Sun
- below the horizon, 4°20' down
- Now
- civil twilight
- Good for sights (15°–65°)
- Moon, Mars, Jupiter, Saturn, 6 bright stars
Twilight: planets and bright stars are out and the horizon is still sharp. The best time for a fix.
- GHA: hour + increment (Sun and planets column) + v correction. v, at the foot of the planet's column, allows for the planet not moving at exactly 15° an hour. It is positive, except sometimes for Venus.
- Dec: hour + d correction, as for the Sun.
- Altitude: the stars and planets column (refraction only). Venus and Mars, being close, also get a small additional correction for parallax.
- A planet that is not where a star should be is the giveaway: check the almanac before naming a bright "star".