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

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.
The :seconds part is optional.

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.
The :seconds part is optional.

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).

skyDistanceRadians( ra1, dec1, ra2, dec2 )
 Calculates the separation (distance around a great circle) of
two points on the sky in radians.

posAngRadians( ra1, dec1, ra2, dec2 )
 Calculates the position angle between two points on the sky in radians.
The result is in the range +/pi.
If point 2 is due east of point 1, the result is +pi/2.
Zero is returned if the points are coincident.

polarDistanceRadians( ra1, dec1, radius1, ra2, dec2, radius2 )
 Calculates the distance in three dimensional space
between two points specified in spherical polar coordinates.

hoursToRadians( hours )
 Converts hours to radians.

degreesToRadians( deg )
 Converts degrees to radians.

radiansToDegrees( rad )
 Converts radians to degrees.

raFK4toFK5radians( 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.

decFK4toFK5radians( 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.

raFK5toFK4radians( 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.

decFK5toFK4radians( 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.

raFK4toFK5Radians( 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.

decFK4toFK5Radians( 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.

raFK5toFK4Radians( 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.

decFK5toFK4Radians( 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.

DEGREE_RADIANS
 The size of one degree in radians.

HOUR_RADIANS
 The size of one hour of right ascension in radians.

ARC_MINUTE_RADIANS
 The size of one arcminute in radians.

ARC_SECOND_RADIANS
 The size of one arcsecond in radians.
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Next: Coverage
Up: General Functions
Previous: Formats
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:
topcatuser@jiscmail.ac.uk