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15.5.458 precess

precess(coords, from, to [, /julian, /besselian])

Precesses the equatorial coordinates coords from the equinox identified by from to the equinox identified by to. coords must be a numerical array and must have at least two elements in its first dimension, which are interpreted as the right ascension and declination, measured in degrees. from and to are interpreted as Julian Dates if no keywords are specified, or as Julian years (e.g., 2000.0 = J2000.0) if /julian is specified, or as semi-Besselian years (e.g., 1950.0 = B1950.0) if /besselian is specified. Besselian years are taken to be 365.2421988 days long, and B1950.0 corresponds to JDE 2433282.4235.

See also: astron, calendar