eqn_of_time.f
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| DOUBLE PRECISION FUNCTION EQN_OF_TIME(MEAN_LONG,IYR) | ||||
| IMPLICIT NONE | ||||
| c | ||||
| c $Revision: 1.1 $ | ||||
| c | ||||
| c Log: eqn_of_time.f,v | ||||
| c Revision 1.4 1997/04/15 16:55:43 baker | ||||
| c Added a bit of code to handle the year 2000 problem. | ||||
| c If the year is less than 88, we assume it is 2000-something. | ||||
| c If the year is between 88 and 99 we assume it is 19xx. | ||||
| c If the year is greater than 100 but less than 1900 we | ||||
| c assume that it is 1900+the value. If the year is | ||||
| c greater then 1900 we assume it is given correctly in | ||||
| c full 4-digit form. | ||||
| c | ||||
| c Revision 1.3 1994/10/17 12:51:20 baker | ||||
| c some code had to be rearranged to convince the compiler it was | ||||
| c really OK. | ||||
| c | ||||
| c Revision 1.2 94/10/17 12:39:41 12:39:41 baker (Kile Baker S1G) | ||||
| c added ephemerides for 1989 - 1998. This also required code to be | ||||
| c added to determine which constants to use. | ||||
| c | ||||
| c Revision 1.1 94/10/14 11:27:56 11:27:56 baker (Kile Baker S1G) | ||||
| c Initial revision | ||||
| C | ||||
| C Imported by Bill Rideout on April 21, 2010 | ||||
| C Modified by nag_apt to convert all reals to double, int16 to ints | ||||
| C | ||||
| C $Id: eqn_of_time.f 3304 2011-01-17 15:25:59Z brideout $ | ||||
| c | ||||
| c | ||||
| SAVE | ||||
| DOUBLE PRECISION MEAN_LONG | ||||
| INTEGER*4 IYR,INDEX | ||||
| DOUBLE PRECISION COEFS(7,10) | ||||
| DATA COEFS/-105.8D0,596.2D0,4.4D0,-12.7D0,-429.0D0,-2.1D0,19.3D0, | ||||
| + -105.9D0,596.2D0,4.4D0,-12.7D0,-429.0D0,-2.1D0,19.3D0, | ||||
| + -106.1D0,596.2D0,4.4D0,-12.7D0,-428.9D0,-2.1D0,19.3D0, | ||||
| + -106.2D0,596.2D0,4.4D0,-12.7D0,-428.9D0,-2.1D0,19.3D0, | ||||
| + -106.4D0,596.1D0,4.4D0,-12.7D0,-428.9D0,-2.1D0,19.3D0, | ||||
| + -106.5D0,596.1D0,4.4D0,-12.7D0,-428.8D0,-2.1D0,19.3D0, | ||||
| + -106.6D0,596.1D0,4.4D0,-12.7D0,-428.8D0,-2.1D0,19.3D0, | ||||
| + -106.7D0,596.1D0,4.4D0,-12.7D0,-428.7D0,-2.1D0,19.3D0, | ||||
| + -106.8D0,596.1D0,4.4D0,-12.7D0,-428.7D0,-2.1D0,19.3D0, | ||||
| + -107.0D0,596.1D0,4.4D0,-12.7D0,-428.7D0,-2.1D0,19.3D0/ | ||||
| c | ||||
| c compute the index into the coeffiecients table from the year | ||||
| c | ||||
| IF (IYR.LT.88) THEN | ||||
| INDEX = IYR + 2000 - 1988 | ||||
| ELSE IF (IYR.GE.88 .AND. IYR.LT.100) THEN | ||||
| INDEX = IYR - 88 | ||||
| ELSE IF (IYR.GE.100 .AND. IYR.LT.1900) THEN | ||||
| INDEX = IYR - 88 | ||||
| ELSE | ||||
| INDEX = IYR - 1988 | ||||
| END IF | ||||
| IF (INDEX.LE.0) INDEX = 1 | ||||
| IF (INDEX.GT.10) INDEX = 10 | ||||
| EQN_OF_TIME = COEFS(1,INDEX)*DSIN(MEAN_LONG) + | ||||
| + COEFS(2,INDEX)*DSIN(2.0D0*MEAN_LONG) + | ||||
| + COEFS(3,INDEX)*DSIN(3.0D0*MEAN_LONG) + | ||||
| + COEFS(4,INDEX)*DSIN(4.0D0*MEAN_LONG) + | ||||
| + COEFS(5,INDEX)*DCOS(MEAN_LONG) + | ||||
| + COEFS(6,INDEX)*DCOS(2.0D0*MEAN_LONG) + | ||||
| + COEFS(7,INDEX)*DCOS(3.0D0*MEAN_LONG) | ||||
| RETURN | ||||
| END | ||||
