Definition
A publication, issued jointly by the U.S. Naval Observatory and Her Majesty's Nautical Almanac Office, that provides tabulated astronomical data — including the Greenwich Hour Angle and declination of the Sun, Moon, planets, and selected stars — at regular time intervals throughout the year. It is used in celestial navigation to determine an aircraft's position from observations of celestial bodies.
Plain English
A reference book of star, Sun, Moon, and planet positions for every day and time of the year. A navigator uses these tables, along with sightings of those bodies, to figure out where the aircraft is.
Context Anchor
Seen in night operations and regulations when determining whether a flight is being made during day, night, or civil twilight.
Derivation
‘Almanac’ comes from Medieval Latin ‘almanachus,’ meaning a calendar or table of astronomical events. ‘Air’ distinguishes this version from the older Nautical Almanac used at sea — the Air Almanac is formatted for the faster pace of flight, with data tabulated at shorter time intervals so an airborne navigator can find values quickly.
Why Pilots Care
Provides a reliable backup method for determining position and heading when electronic navigation systems are unavailable or unreliable.
Intuition Check
Do not read “Air Almanac” as a general flying handbook. Here it means a specific yearly reference for official sky and daylight data used in aviation.
Example Sentence 1
Before the long over-water leg, the navigator pulled out the Air Almanac to look up the Sun's position for the planned time of the next sextant shot.
Example Sentence 2
During the overwater ferry flight, the crew used data from the Air Almanac to verify their position with star observations.