In astronomy as the angular distance on the celestial sphere measured westward along the celestial equator from the meridian to the hour circle passing through a point

In astronomy, hour angle is defined as the angular distance on the celestial sphere measured westward along the celestial equator from the meridian to the hour circle passing through a point.

one of the coordinates used in the equatorial coordinate system to give the direction of a point on the celestial sphere

In astronomy and celestial navigation, the hour angle is one of the coordinates used in the equatorial coordinate system to give the direction of a point on the celestial sphere.

the angle between two planes

The hour angle of a point is the angle between two planes: one containing Earth's axis and the zenith (the meridian plane), and the other containing Earth's axis and the given point (the hour circle passing through the point).

a musical performance generated by the movement of the sun

Hour Angle is a musical performance generated by the movement of the sun.

the angle, taken to be positive to the west

Hour angle is the angle, taken to be positive to the west, measured along the celestial equator between an observer’s meridian and the hour circle on which some celestial point or object lies.

of measuring the time since upper culmination

Hour angle may be considered a means of measuring the time since upper culmination, the moment when an object contacts the meridian overhead.

1 turn/24 or 15°

1 Hour angle is 1 turn/24 or 15°.

as the difference between noon and the desired time of the day

The hour angle is defined as the difference between noon and the desired time of the day.

the angular displacement of the sun east or west of the local meridian due to rotation of the earth on the earth's axis at 15° per hour with morning being negative and afternoon being positive

: The hour angle is the angular displacement of the sun east or west of the local meridian due to rotation of the earth on the earth's axis at 15° per hour with morning being negative and afternoon being positive.

between a fixed point of reference and a point on the globe, measured East or West

The hour angle is the angle between a fixed point of reference and a point on the globe, measured East or West.

a way of measuring a celestial object’s “longitude” in terms of time

■ 22D: HOUR ANGLE is a way of measuring a celestial object’s “longitude” in terms of time.

The angle between the meridian plane of the observer and the meridian plane of a celestial object, measured from east to west

The angle between the meridian plane of the observer and the meridian plane of a celestial object, measured from east to west, is called the hour angle of the object.

minutes, and seconds

A body's hour angle is measured in hours, minutes, and seconds, and corresponds to seconds's right ascension as measured with respect to the observer's meridian (which changes with time) rather than the vernal equinox (which is fixed on the celestial equator).

into the number of degrees which the sun moves across the sky

The Hour Angle converts the local solar time (LST) into the number of degrees which the sun moves across the sky.

the angle along the celestial equator from the observer's meridian

The Hour angle measures the angle along the celestial equator from the observer's meridian to the hour circle passing through the sun.

an intermediate value used during the calculation of the DEC and Ra

Hour angle is an intermediate value used during the calculation of the DEC and Ra and is shown for interest only.

The angle measured westward from this meridian to the hour circle

The angle measured westward from this meridian to the hour circle is called the hour angle (HA) of the star.