The date and time for which to find horizontal coordinates.
The location of the observer for which to find horizontal coordinates.
Right ascension in sidereal hours of the celestial object, referred to the mean equinox of date for the J2000 epoch.
Declination in degrees of the celestial object, referred to the mean equator of date for the J2000 epoch. Positive values are north of the celestial equator and negative values are south.
Optionalrefraction: stringIf omitted or has a false-like value (false, null, undefined, etc.)
the calculations are performed without any correction for atmospheric
refraction. If the value is the string "normal",
uses the recommended refraction correction based on Meeus "Astronomical Algorithms"
with a linear taper more than 1 degree below the horizon. The linear
taper causes the refraction to linearly approach 0 as the altitude of the
body approaches the nadir (-90 degrees).
If the value is the string "jplhor", uses a JPL Horizons
compatible formula. This is the same algorithm as "normal",
only without linear tapering; this can result in physically impossible
altitudes of less than -90 degrees, which may cause problems for some applications.
(The "jplhor" option was created for unit testing against data
generated by JPL Horizons, and is otherwise not recommended for use.)
Converts equatorial coordinates to horizontal coordinates.
Given a date and time, a geographic location of an observer on the Earth, and equatorial coordinates (right ascension and declination) of a celestial body, returns horizontal coordinates (azimuth and altitude angles) for that body as seen by that observer. Allows optional correction for atmospheric refraction.