Equinox Conversion

Equinox conversion

Algorithms

Converts ecliptic coordinates for the moving equinox.

Unit

moon_aux

procedure ConvertEquinox(source_date, target_date: TDateTime; var rektaszension, declination: extended);

procedure ConvertEquinoxB1950toJ2000(var rektaszension, declination: extended);

procedure ConvertEquinoxDateToJ2000(date: TDateTime; var rektaszension, declination: extended);

procedure ConvertEquinoxJ2000toDate(date: TDateTime; var rektaszension, declination: extended);

Description

Due to the precession of the earth rotational axis the equinox moves along the ecliptic by about 50" per year. Thus ecliptic coordinates need the reference date for their full definition, either they are calculated with the equinox of the date, or with one of the standard frames J2000 or B1950.

Reference

These functions are based upon chapter 21 (20) of "Astronomical Algorithms".