Finds the hour angle of a body for a given observer and time. The hour angle indicates the body's position in the sky with respect to Earth's rotation.
Arguments
- body
Integer body code (see astro_body).
- time
A
POSIXctdate/time in UTC.- latitude
Observer's geographic latitude in degrees.
- longitude
Observer's geographic longitude in degrees.
- height
Observer's height above sea level in metres. Default
0.
Value
A numeric value representing the hour angle in the range [0, 24), where each unit is one sidereal hour.
Details
The hour angle is 0 when the body culminates (reaches its highest point), and increases by 1 unit for every sidereal hour that passes. A value of 12 means the body is at its lowest point. A value of 24 is equivalent to 0.
Examples
t <- as.POSIXct("2025-06-21 12:00:00", tz = "UTC")
astro_hour_angle(astro_body[["SUN"]], t,
latitude = -33.8688, longitude = 151.2093)
#> [1] 10.04974