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diff --git a/noao/astutil/asttools/README b/noao/astutil/asttools/README new file mode 100644 index 00000000..dbdb7d67 --- /dev/null +++ b/noao/astutil/asttools/README @@ -0,0 +1,137 @@ +Astronomical Tools: + +Precession: These routines probably have some history even before the + authors quoted as original sources. They have been collected and + some rewritten into SPP by F. Valdes (NOAO), March 1986. PRECES.F + was used originally in V2.3-V2.5 IRAF by George Jacoby. It has + been replaced by ASTPRECESS.X which is the only procedure in the + library. + + astprecess.x -- Precession written by F. Valdes based on Astronomical + Almanac using new IAU system. + precessmgb.x -- Precession + aberration + nutation based on the work of + Manchester, Gordon, and Ball + precessgj.x -- Originally written by G. Jacoby in Fortran and distributed + with V2.3-V2.5 IRAF. Transcribed to SPP by F. Valdes + + Notes: + 1. The differences between ASTPRECESS.X and PRECESSGJ.X ( + and a routine written by D. Wells for the Cyber and later + used in other NOAO software) are on the order of a few + tenths of a second of arc. I believe the differences are + due to using 1984 almanac methods in the former and much + earlier methods for the latter. + 3. PRECESSMGB.X differs considerably from the others to the order + of many seconds of arc. It does include other effects not + present in the other routines. It totally fails at DEC=+-90. + It is based on roughly 1970 almanac methods. + 4. See PRECESS.DOC for comparison. + +Radial Velocity: These formulas for these routines were partly obtained + by inspection of the code for the subroutine DOP in the program DOPSET + written by R. N. Manchester and M. A. Gordon of NRAO dated January 1970. + They have been restructured, revised, and coded in SPP by F. Valdes. + + astvr.x -- Project a velocity vector in radial velocity along line of sight. + astvbary.x -- Radial velocity component of center of the Earth relative to + to the barycenter of the Earth-Moon system. + astvrotate.x -- Radial velocity component of the observer relative to + the center of the Earth due to the Earth's rotation. + astvorbit.x -- Radial velocity component of the observer relative to + the center of the Earth due to the Earth's rotation. + astvsun.x -- Projection of the sun's velocity along the given direction. + +Coordinates: + + astarcsep.x -- Arc distance (arcsec) between two spherical coordinates + (hours, degrees). + astcoord.x -- This procedure converts the longitude-latitude coordinates + (a1, b1) of a point on a sphere into corresponding coordinates + (a2, b2) in a different coordinate system that is specified by + the coordinates of its origin (ao, bo) and its north pole (ap, + bp) in the original coordinate system. The range of a2 will be + from -pi to pi. + astgalactic.x -- Convert equatorial coordinates (1950) to galactic + coordinates. + astgaltoeq.x -- Convert galactic coordinates to equitorial (1950). + +Dates and times: + + asttimes.x: + AST_DATE_TO_EPOCH -- Convert Gregorian date and solar mean time to + a Julian epoch. A Julian epoch has 365.25 days per year and 24 + hours per day. + AST_EPOCH_TO_DATE -- Convert a Julian epoch to year, month, day, and + time. + AST_DAY_OF_YEAR -- The day number for the given year is returned. + AST_DAY_OF_WEEK -- Return the day of the week for the given Julian day. + The integer day of the week is 0=Sunday - 6=Saturday. The + character string is the three character abbreviation for the day + of the week. Note that the day of the week is for Greenwich + if the standard UT is used. + AST_JULDAY -- Convert epoch to Julian day. + AST_DATE_TO_JULDAY -- Convert date to Julian day. + AST_JULDAY_TO_DATE -- Convert Julian day to date. + AST_MST -- Mean sidereal time of the epoch at the given longitude. + This procedure may be used to optain Greenwich Mean Sidereal Time + (GMST) by setting the longitude to 0. + asthjd.x: + AST_HJD -- Helocentic Julian Day for a direction of observation. + AST_JD_TO_HJD -- Helocentic Julian Day for a direction of observation. + +Helocentric Parameters: + + astdsun.x: + AST_DSUN - Distance to Sun in AU. + +Misc: + + astlvac.x: + AST_LVAC - Convert air wavelengths to vacuum wavelengths (Angstroms) + +Y2K: + Most routines work in Julian days or epochs. If they have an input + year it is converted to one of these forms by calling + ast_date_to_julday. This is the only routine that has a Y2K + connection. It assumes two digit years are 20th century. These + routines are Y2K correct. + + +The following are the comments and references from the DOPSET program +noted above. The HJD routine was also derived from this code. + +C MODIFIED FOR IBM 360 BY R.N.MANCHESTER AND M.A.GORDON +C JANUARY 1970 +C +C +C DOP CALCULATES THE VELOCITY COMPONENT OF THE OBSERVER WITH RESPECT +C TO THE LOCAL STANDARD OF REST AS PROJECTED ONTO A LINE SPECIFIED BY T +C ASCENSION AND DECLINATION (RAHRS, RAMIN, RASEC, DDEG, DMIN, DSEC) EPO +C DATE, FOR A TIME SPECIFIED AS FOLLOWS: NYR = LAST TWO DIGITS OF THE +C (FOR 19XX A.D.), NDAY = DAY NUMBER (GMT), NHUT, NMUT, NSUT = HRS, MIN +C (GMT). THE LOCATION OF THE OBSERVER IS SPECIFIED BY THE LATITUDE (AL +C LONGITUDE (OLONG) (GEODETIC) (IN DEGREES) AND ELEVATION (ELEV) (IN ME +C ABOVE MEAN SEA LEVEL. THE SUBROUTINE OUTPUTS THE LOCAL MEAN SIDEREAL +C (XLST IN DAYS), THE COMPONENT OF THE SUN*S MOTION WITH RESPECT TO THE +C STANDARD OF REST AS PROJECTED ONTO THE LINE OF SIGHT TO THE SOURCE (V +C KM/SEC) AS WELL AS THE TOTAL VELOCITY COMPONENT V1 (KM/SEC). POSITIV +C VELOCITY CORRESPONDS TO INCREASING DISTANCE BETWEEN SOURCE AND OBSERV +C +C THIS VERSION OF DOP TAKES INTO ACCOUNT COMPONENTS OF THE OBSERVER*S +C MOTION DUE TO THE ROTATION OF THE EARTH, THE REVOLUTION OF THE EARTH- +C BARYCENTER ABOUT THE SUN, AND THE MOTION OF THE EARTH*S CENTER ABOUT +C EARTH-MOON BARYCENTER. THE PERTURBATIONS OF THE EARTH*S ORBIT DUE TO +C PLANETS ARE NEGLECTED. THE ABSOLUTE PRECISION OF THIS VERSION OF DOP +C ABOUT 0.004 KM/SEC, BUT SINCE THE DOMINANT ERROR TERM IS SLOWLY VARYI +C RELATIVE ERROR WILL BE CONSIDERABLY LESS FOR TIMES UP TO A WEEK OR SO +C +C REFERENCES: MCRAE, D. A., WESTERHOUT, G., TABLE FOR THE REDUCTION OF +C VELOCITIES TO THE LOCAL STANDARD OF REST, THE OBSERVAY=2. +C LUND, SWEDEN, 1956. +C SMART, W. M., TEXT-BOOK ON SPHERICAL ASTRONOMY, CAMBRIDG +C UNIV. PRESS, 1962. +C THE AMERICAN EPHEMERIS AND NAUTICAL ALMANAC +C THE SUPPLEMENT TO THE ABOVE +C +C VERSION OF JUNE 1969 + |