jsky.coords

Class JPrec

java.lang.Object

jsky.coords.JPrec

public class JPrec
extends Object

Precession of Coordinates in new IAU system.

This class is based on C routintes by Francois Ochsenbein [ESO-IPG]. It uses the IAU 76 precession constants and assumes the FK5 system.

Precession constants are taken from Lederle and Schwan (Astron. Astrophys. 134, 1, 1984), Liske J.H. (Astron. Astrophys. 73, 282, 1979). Dates must be expressed in Julian Years.

The precession may be applied on unit vectors (mnemonic u), or on equatorial coordinates (mnemonic q).

Constructor Summary

Constructors

Constructor and Description
JPrec()

Method Summary

Modifier and Type	Method and Description
static void	prej_q(double[] q0, double[] q1, double eq0, double eq1) Performs a complete precession between 2 equinoxes.
static void	prej_R(double[][] R, double eq0, double eq1) Compute the precession matrix, using the new IAU constants.
static void	prej_u(double[] u0, double[] u1, double eq0, double eq1) Performs a complete precession between 2 equinoxes.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

JPrec

public JPrec()

Method Detail

prej_R

public static void prej_R(double[][] R,
                          double eq0,
                          double eq1)

Compute the precession matrix, using the new IAU constants. (IAU 1976). The resulting matrix is such that u(t_1) = R * u(t_0) (old to new frame).

Parameters:

R - OUT: rotation matrix

eq0 - IN: Initial equinox (Julian Years)

eq1 - IN: Final equinox (Julian Years)

prej_q

public static void prej_q(double[] q0,
                          double[] q1,
                          double eq0,
                          double eq1)

Performs a complete precession between 2 equinoxes. Use the new IAU constants. Compute the precession rotation matrix if necessary, then apply the rotation.

Parameters:

q0 - IN: ra+dec at equinox eq0 in degrees

q1 - OUT: precessed to equinox eq1

eq0 - IN: Initial equinox (Julian Years)

eq1 - IN: Final equinox (Julian Years)

prej_u

public static void prej_u(double[] u0,
                          double[] u1,
                          double eq0,
                          double eq1)

Performs a complete precession between 2 equinoxes. Use the new IAU constants. Compute the precession rotation matrix if necessary, then apply the rotation.

Parameters:

u0 - IN: Unit vector at equinox eq0

u1 - OUT: precessed to equinox eq1

eq0 - IN: Initial equinox (Julian Years)

eq1 - IN: Final equinox (Julian Years)