Anomalistic Month. Time taken by Moon to go from perigee to perigee. Interval is about 27.55455 days.
Anomalistic Period of Planet. Time taken by a planet to go from perihelion to perihelion. Interval is irregular through movement of perihelion point.
Anschutz Gyro Compass.German type in which three gyros revolve in air. Sensitive element floats in a mercury bath. Damping is effected by oil.
Answer the Helm. A ship is said to do this when she alters her direction in response to movements of tiller and rudder.
Antarctic.Region of Earth's surface south of latitude 66° 33' S. Pertaining to this region. Antarctic Circle. Region enclosed by parallel 66° 33' S. Name is often given to the parallel itself.
Antares. Star α Scorpio. S.H.A. 113°; Dec. S 26°; Mag. 1.2. Diameter is 430 times that of Sun; temperature 3100°A. Name means 'rivalling Mars'—in the redness of its colour. Antecians. People living in same latitude and longitude, but on opposite sides of Equator. They have same length of days, but at opposite times of the year. Antedate. To date a document so that its effect counts as from a date previous to the date of signing.
Ante Meridiem.Between midnight and noon. Before midday (Latin).
Antenna. Arrangement of wires for sending or receiving radio waves.