Definition:Hour Angle

Definition

Let $P$ be a point on the celestial sphere.

The hour angle of $P$ is the angular distance measured westwards along the celestial equator from the vernal equinox.

That is, it is the angular distance measured westwards along the celestial equator between the observer's meridian and the hour circle of $P$.

This is usually denoted $t$.

It is sometimes used instead of right ascension, which is the same thing as hour angle but measured eastwards.

Also see

• Results about hour angle can be found here.

Sources

• 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): equatorial coordinate system
• 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): hour angle (HA)
• 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): right ascension (RA)
• 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): equatorial coordinate system
• 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): hour angle (HA)
• 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): right ascension (RA)