4.4.3 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.

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.

• rad (floating point): angle in radians

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.

• rad (floating point): angle in radians
• secFig (integer): 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.

• rad (floating point): angle in radians

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.

• rad (floating point): angle in radians
• secFig (integer): 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.

• dms (String): formatted DMS string

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.

• hms (String): formatted HMS string

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.

• deg (floating point): degrees part of angle
• min (floating point): minutes part of angle
• sec (floating point): seconds part of angle

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).

• hour (floating point): degrees part of angle
• min (floating point): minutes part of angle
• sec (floating point): seconds part of angle

skyDistance( ra1, dec1, ra2, dec2 )

Calculates the separation (distance around a great circle) of two points on the sky.

• ra1 (floating point): right ascension of point 1 in radians
• dec1 (floating point): declination of point 1 in radians
• ra2 (floating point): right ascension of point 2 in radians
• dec2 (floating point): declination of point 2 in radians

skyDistanceDegrees( ra1, dec1, ra2, dec2 )

Calculates the separation (distance around a great circle) of two points on the sky in degrees.

• ra1 (floating point): right ascension of point 1 in degrees
• dec1 (floating point): declination of point 1 in degrees
• ra2 (floating point): right ascension of point 2 in degrees
• dec2 (floating point): declination of point 2 in degrees

hoursToRadians( hours )

Converts hours to radians.

• hours (floating point): angle in hours

degreesToRadians( deg )

Converts degrees to radians.

• deg (floating point): angle in degrees

radiansToDegrees( rad )

Converts radians to degrees.

• rad (floating point): angle in radians

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.

• raFK4 (floating point): right ascension in B1950.0 FK4 system (radians)
• decFK4 (floating point): declination in B1950.0 FK4 system (radians)

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.

• raFK4 (floating point): right ascension in B1950.0 FK4 system (radians)
• decFK4 (floating point): declination in B1950.0 FK4 system (radians)

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.

• raFK5 (floating point): right ascension in J2000.0 FK5 system (radians)
• decFK5 (floating point): declination in J2000.0 FK5 system (radians)

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.

• raFK5 (floating point): right ascension in J2000.0 FK5 system (radians)
• decFK5 (floating point): declination in J2000.0 FK5 system (radians)

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.

• raFK4 (floating point): right ascension in B1950.0 FK4 system (radians)
• decFK4 (floating point): declination in B1950.0 FK4 system (radians)
• bepoch (floating point): Besselian epoch

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.

• raFK4 (floating point): right ascension in B1950.0 FK4 system (radians)
• decFK4 (floating point): declination in B1950.0 FK4 system (radians)
• bepoch (floating point): Besselian epoch

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.

• raFK5 (floating point): right ascension in J2000.0 FK5 system (radians)
• decFK5 (floating point): declination in J2000.0 FK5 system (radians)
• bepoch (floating point): Besselian epoch

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.

• raFK5 (floating point): right ascension in J2000.0 FK5 system (radians)
• decFK5 (floating point): declination in J2000.0 FK5 system (radians)
• bepoch (floating point): Besselian epoch