Package skyview.geometry.csys
Class Julian
java.lang.Object
skyview.geometry.CoordinateSystem
skyview.geometry.csys.Julian
- All Implemented Interfaces:
Serializable
,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:
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Field Summary
Fields inherited from class skyview.geometry.CoordinateSystem
B1950, Gal, ICRS, J2000
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionGet a description of the object.getName()
Get the name of this object.Return the rotation associated with the coordinate system.Get the Julian Precession Matrix for a given epoch (from J2000).Methods inherited from class skyview.geometry.CoordinateSystem
factory, factory, getSphereDistorter
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Constructor Details
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Julian
public Julian(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).
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Method Details
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getName
Get the name of this object. -
getDescription
Get a description of the object.- Specified by:
getDescription
in interfaceComponent
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getRotater
Return the rotation associated with the coordinate system.- Specified by:
getRotater
in classCoordinateSystem
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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.
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