catran Subroutine

public subroutine catran(it, date1, ra1, dec1, pmra1, pmdec1, parx1, rv1, date2, ra2, dec2, pmra2, pmdec2, parx2, rv2)

THIS SUBROUTINE TRANSFORMS A STAR'S CATALOG QUANTITIES FOR A CHANGE OF EPOCH AND/OR EQUATOR AND EQUINOX. IT CAN ALSO BE USED TO ROTATE CATALOG QUANTITIES ON THE DYNAMICAL EQUATOR AND EQUINOX OF J2000.0 TO THE ICRS OR VICE VERSA.

 IT     = TRANSFORMATION OPTION (IN)
          SET IT=1 TO CHANGE EPOCH (SAME EQUATOR AND EQUINOX)
          SET IT=2 TO CHANGE EQUATOR AND EQUINOX (SAME EPOCH)
          SET IT=3 TO CHANGE EQUATOR AND EQUINOX AND EPOCH
          SET IT=4 TO CHANGE EQUATOR AND EQUINOX OF J2000.0
                   TO ICRS
          SET IT=5 TO CHANGE ICRS TO EQUATOR AND EQUINOX OF
                   J2000.0
 DATE1  = TT JULIAN DATE, OR YEAR, OF ORIGINAL CATALOG
          DATA (THE FOLLOWING SIX ARGUMENTS) (IN)
 RA1    = ORIGINAL MEAN RIGHT ASCENSION IN HOURS (IN)
 DEC1   = ORIGINAL MEAN DECLINATION IN DEGREES (IN)
 PMRA1  = ORIGINAL PROPER MOTION IN RA
          IN MILLIARCSECONDS/YEAR (IN)
 PMDEC1 = ORIGINAL PROPER MOTION IN DEC
          IN MILLIARCSECONDS/YEAR (IN)
 PARX1  = ORIGINAL PARALLAX IN MILLIARCSECONDS (IN)
 RV1    = ORIGINAL RADIAL VELOCITY IN KILOMETERS/SECOND
          (IN)
 DATE2  = TT JULIAN DATE, OR YEAR, FOR TRANSFORMED
          OUTPUT DATA (THE FOLLOWING SIX ARGUMENTS) (IN)
 RA2    = TRANSFORMED MEAN RIGHT ASCENSION IN HOURS (OUT)
 DEC2   = TRANSFORMED MEAN DECLINATION IN DEGREES (OUT)
 PMRA2  = TRANSFORMED PROPER MOTION IN RA
          IN MILLIARCSECONDS/YEAR (OUT)
 PMDEC2 = TRANSFORMED PROPER MOTION IN DEC
          IN MILLIARCSECONDS/YEAR (OUT)
 PARX2  = TRANSFORMED PARALLAX IN MILLIARCSECONDS (OUT)
 RV2    = TRANSFORMED RADIAL VELOCITY IN KILOMETERS/SECOND
          (OUT)

NOTE 1: DATE1 AND DATE2 MAY BE SPECIFIED EITHER AS A JULIAN DATE (E.G., 2433282.5D0) OR A JULIAN YEAR AND FRACTION (E.G., 1950.0D0). VALUES LESS THAN 10000 ARE ASSUMED TO BE YEARS. FOR IT=2 OR IT=3, EITHER DATE1 OR DATE2 MUST BE 2451545.0 OR 2000.0 (J2000.0). FOR IT=4 AND IT=5, DATE1 AND DATE2 ARE IGNORED.

NOTE 2: IT=1 UPDATES THE STAR'S DATA TO ACCOUNT FOR THE STAR'S SPACE MOTION BETWEEN THE FIRST AND SECOND DATES, WITHIN A FIXED REFERENCE SYSTEM. IT=2 APPLIES A ROTATION OF THE REFERENCE SYSTEM CORRESPONDING TO PRECESSION BETWEEN THE FIRST AND SECOND DATES, BUT LEAVES THE STAR FIXED IN SPACE. IT=3 PROVIDES BOTH TRANSFORMATIONS. IT=4 AND IT=5 PROVIDE A A FIXED ROTATION ABOUT VERY SMALL ANGLES (<0.1 ARCSECOND) TO TAKE DATA FROM THE DYNAMICAL SYSTEM OF J2000.0 TO THE ICRS (IT=4) OR VICE VERSA (IT=5).

NOTE 3: FOR IT=1, INPUT DATA CAN BE IN ANY FIXED REFERENCE SYSTEM. FOR IT=2 OR IT=3, THIS SUBROUTINE ASSUMES THE INPUT DATA IS IN THE DYNAMICAL SYSTEM AND PRODUCES OUTPUT IN THE DYNAMICAL SYSTEM. FOR IT=4, THE INPUT DATA MUST BE ON THE DYNAMICAL EQUATOR AND EQUINOX OF J2000.0. FOR IT=5, THE INPUT DATA MUST BE IN THE ICRS.

NOTE 4: THIS SUBROUTINE CANNOT BE PROPERLY USED TO BRING DATA FROM OLD STAR CATALOGS INTO THE MODERN SYSTEM, BECAUSE OLD CATALOGS WERE COMPILED USING A SET OF CONSTANTS THAT ARE INCOMPATIBLE WITH MODERN VALUES. IN PARTICULAR, IT SHOULD NOT BE USED FOR CATALOGS WHOSE POSITIONS AND PROPER MOTIONS WERE DERIVED BY ASSUMING A PRECESSION CONSTANT SIGNIFICANTLY DIFFERENT FROM THE VALUE IMPLICIT IN SUBROUTINE PRECES.

Arguments