skyview.geometry.csys
Class JulianCoordinateSystem

java.lang.Object
  skyview.geometry.CoordinateSystem
      skyview.geometry.csys.JulianCoordinateSystem

All Implemented Interfaces:

java.io.Serializable, Component

public class JulianCoordinateSystem
extends CoordinateSystem
implements Component

The class defining Julian coordinate systems. The reference coordinate system is J2000. We use the FK5 coordinate frame as the realization of the Julian coordinate system. At the 50 milliarcsecond level this is not valid: There is an offset of J2000 and FK5. However the details of this offset are still somewhat unclear, so we use the better defined frame.

See Also:

Serialized Form

Field Summary

Fields inherited from class skyview.geometry.CoordinateSystem

B1950, Galactic, ICRS, J2000

Constructor Summary

JulianCoordinateSystem(double epoch)
Get a Julian CoordinateSystem of a given epoch.

Method Summary

java.lang.String	getDescription() Get a description of the object.
java.lang.String	getName() Get the name of this object.
Rotater	getRotater() Return the rotation associated with the coordinate system.
Rotater	precession() Get the Julian Precession Matrix for a given epoch (from J2000).

Methods inherited from class skyview.geometry.CoordinateSystem

factory, factory, getSphereDistorter

Methods inherited from class java.lang.Object

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

Constructor Detail

JulianCoordinateSystem

public JulianCoordinateSystem(double epoch)

Get a Julian CoordinateSystem of a given epoch.

Parameters:

epoch - The epoch of the equinox of the coordinates in calendar years (possibly fractional).

Method Detail

getName

public java.lang.String getName()

Get the name of this object.

Specified by:

getName in interface Component

getDescription

public java.lang.String getDescription()

Get a description of the object.

Specified by:

getDescription in interface Component

getRotater

public Rotater getRotater()

Return the rotation associated with the coordinate system.

Specified by:

getRotater in class CoordinateSystem

precession

public Rotater precession()

Get the Julian Precession Matrix for a given epoch (from J2000). Approach based on P.Wallace's SLA library. The equations are available in Kaplan, USNO Circular 163, 1981, page A2. Here we assume in these equations we assume T=0 so that we are doing a transformation between J2000 and the specified ending epoch.