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### B.1.11 Coords

Functions for angle transformations and manipulations. In particular, methods for translating between radians and HH:MM:SS.S or DDD:MM:SS.S type sexagesimal representations are provided.

DEGREE
  The size of one degree in radians.
HOUR
  The size of one hour of right ascension in radians.
ARC_MINUTE
  The size of one arcminute in radians.
ARC_SECOND
  The size of one arcsecond in radians.
radiansToDms( rad )
  Converts an angle in radians to a formatted degrees:minutes:seconds string. No fractional part of the seconds field is given.
radiansToDms( rad, secFig )
  Converts an angle in radians to a formatted degrees:minutes:seconds string with a given number of decimal places in the seconds field.
radiansToHms( rad )
  Converts an angle in radians to a formatted hours:minutes:seconds string. No fractional part of the seconds field is given.
radiansToHms( rad, secFig )
  Converts an angle in radians to a formatted hours:minutes:seconds string with a given number of decimal places in the seconds field.
dmsToRadians( dms )
  Converts a formatted degrees:minutes:seconds string to an angle in radians. Delimiters may be colon, space, characters `dm[s]`, or some others. Additional spaces and leading +/- are permitted.
hmsToRadians( hms )
  Converts a formatted hours:minutes:seconds string to an angle in radians. Delimiters may be colon, space, characters `hm[s]`, or some others. Additional spaces and leading +/- are permitted.
dmsToRadians( deg, min, sec )
  Converts degrees, minutes, seconds to an angle in radians.

  In conversions of this type, one has to be careful to get the sign right in converting angles which are between 0 and -1 degrees. This routine uses the sign bit of the `deg` argument, taking care to distinguish between +0 and -0 (their internal representations are different for floating point values). It is illegal for the `min` or `sec` arguments to be negative.

hmsToRadians( hour, min, sec )
  Converts hours, minutes, seconds to an angle in radians.

  In conversions of this type, one has to be careful to get the sign right in converting angles which are between 0 and -1 hours. This routine uses the sign bit of the `hour` argument, taking care to distinguish between +0 and -0 (their internal representations are different for floating point values).

skyDistance( ra1, dec1, ra2, dec2 )
  Calculates the separation (distance around a great circle) of two points on the sky.
skyDistanceDegrees( ra1, dec1, ra2, dec2 )
  Calculates the separation (distance around a great circle) of two points on the sky in degrees.
hoursToRadians( hours )
  Converts hours to radians.
degreesToRadians( deg )
  Converts degrees to radians.
radiansToDegrees( rad )
  Converts radians to degrees.
raFK4toFK5( raFK4, decFK4 )
  Converts a B1950.0 FK4 position to J2000.0 FK5 at an epoch of B1950.0 yielding Right Ascension. This assumes zero proper motion in the FK5 frame.
decFK4toFK5( raFK4, decFK4 )
  Converts a B1950.0 FK4 position to J2000.0 FK5 at an epoch of B1950.0 yielding Declination This assumes zero proper motion in the FK5 frame.
raFK5toFK4( raFK5, decFK5 )
  Converts a J2000.0 FK5 position to B1950.0 FK4 at an epoch of B1950.0 yielding Declination. This assumes zero proper motion, parallax and radial velocity in the FK5 frame.
decFK5toFK4( raFK5, decFK5 )
  Converts a J2000.0 FK5 position to B1950.0 FK4 at an epoch of B1950.0 yielding Declination. This assumes zero proper motion, parallax and radial velocity in the FK5 frame.
raFK4toFK5( raFK4, decFK4, bepoch )
  Converts a B1950.0 FK4 position to J2000.0 FK5 yielding Right Ascension. This assumes zero proper motion in the FK5 frame. The `bepoch` parameter is the epoch at which the position in the FK4 frame was determined.
decFK4toFK5( raFK4, decFK4, bepoch )
  Converts a B1950.0 FK4 position to J2000.0 FK5 yielding Declination. This assumes zero proper motion in the FK5 frame. The `bepoch` parameter is the epoch at which the position in the FK4 frame was determined.
raFK5toFK4( raFK5, decFK5, bepoch )
  Converts a J2000.0 FK5 position to B1950.0 FK4 yielding Declination. This assumes zero proper motion, parallax and radial velocity in the FK5 frame.
decFK5toFK4( raFK5, decFK5, bepoch )
  Converts a J2000.0 FK5 position to B1950.0 FK4 yielding Declination. This assumes zero proper motion, parallax and radial velocity in the FK5 frame.

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TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page: http://www.starlink.ac.uk/topcat/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@bristol.ac.uk