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SkyFrame - Celestial coordinate system description   

Description:
A SkyFrame is a specialised form of Frame which describes celestial longitude/latitude coordinate systems. The particular celestial coordinate system to be represented is specified by setting the SkyFrame's System attribute (currently, the default is FK5) qualified, as necessary, by a mean Equinox value and/or an Epoch.

All the coordinate values used by a SkyFrame are in radians. These may be formatted in more conventional ways for display by using AST_FORMAT.

Constructor Function:
AST_SKYFRAME

Inheritance
The SkyFrame class inherits from the Frame class.

Attributes
In addition to those attributes common to all Frames, every SkyFrame also has the following attributes:

  • AsTime(axis): Format celestial coordinates as times?
  • Equinox: Epoch of the mean equinox
  • LatAxis: Index of the latitude axis
  • LonAxis: Index of the longitude axis
  • NegLon: Display longitude values in the range [-pi,pi]?
  • Projection: Sky projection description.

Functions
The SkyFrame class does not define any new routines beyond those which are applicable to all Frames.



next up previous
Next: SlaMap - Sequence of celestial coordinate conversions
Up: AST Class Descriptions
Previous: SkyAxis - Store celestial axis information

AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 210
R.F. Warren-Smith & D.S. Berry
30th April 2003
E-mail:ussc@star.rl.ac.uk

Copyright (C) 2003 Central Laboratory of the Research Councils