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/*
*+
* Name:
* palOap
* Purpose:
* Observed to apparent place
* Language:
* Starlink ANSI C
* Type of Module:
* Library routine
* Invocation:
* void palOap ( const char *type, double ob1, double ob2, double date,
* double dut, double elongm, double phim, double hm,
* double xp, double yp, double tdk, double pmb,
* double rh, double wl, double tlr,
* double *rap, double *dap );
* Arguments:
* type = const char * (Given)
* Type of coordinates  'R', 'H' or 'A' (see below)
* ob1 = double (Given)
* Observed Az, HA or RA (radians; Az is N=0;E=90)
* ob2 = double (Given)
* Observed ZD or Dec (radians)
* date = double (Given)
* UTC date/time (Modified Julian Date, JD2400000.5)
* dut = double (Given)
* delta UT: UT1UTC (UTC seconds)
* elongm = double (Given)
* Mean longitude of the observer (radians, east +ve)
* phim = double (Given)
* Mean geodetic latitude of the observer (radians)
* hm = double (Given)
* Observer's height above sea level (metres)
* xp = double (Given)
* Polar motion xcoordinates (radians)
* yp = double (Given)
* Polar motion ycoordinates (radians)
* tdk = double (Given)
* Local ambient temperature (K; std=273.15)
* pmb = double (Given)
* Local atmospheric pressure (mb; std=1013.25)
* rh = double (Given)
* Local relative humidity (in the range 0.01.0)
* wl = double (Given)
* Effective wavelength (micron, e.g. 0.55)
* tlr = double (Given)
* Tropospheric laps rate (K/metre, e.g. 0.0065)
* rap = double * (Given)
* Geocentric apparent right ascension
* dap = double * (Given)
* Geocentric apparent declination
* Description:
* Observed to apparent place.
* Authors:
* PTW: Patrick T. Wallace
* TIMJ: Tim Jenness (JAC, Hawaii)
* {enter_new_authors_here}
* Notes:
*  Only the first character of the TYPE argument is significant.
* 'R' or 'r' indicates that OBS1 and OBS2 are the observed right
* ascension and declination; 'H' or 'h' indicates that they are
* hour angle (west +ve) and declination; anything else ('A' or
* 'a' is recommended) indicates that OBS1 and OBS2 are azimuth
* (north zero, east 90 deg) and zenith distance. (Zenith
* distance is used rather than elevation in order to reflect the
* fact that no allowance is made for depression of the horizon.)
*
*  The accuracy of the result is limited by the corrections for
* refraction. Providing the meteorological parameters are
* known accurately and there are no gross local effects, the
* predicted apparent RA,Dec should be within about 0.1 arcsec
* for a zenith distance of less than 70 degrees. Even at a
* topocentric zenith distance of 90 degrees, the accuracy in
* elevation should be better than 1 arcmin; useful results
* are available for a further 3 degrees, beyond which the
* palRefro routine returns a fixed value of the refraction.
* The complementary routines palAop (or palAopqk) and palOap
* (or palOapqk) are selfconsistent to better than 1 micro
* arcsecond all over the celestial sphere.
*
*  It is advisable to take great care with units, as even
* unlikely values of the input parameters are accepted and
* processed in accordance with the models used.
*
*  "Observed" Az,El means the position that would be seen by a
* perfect theodolite located at the observer. This is
* related to the observed HA,Dec via the standard rotation, using
* the geodetic latitude (corrected for polar motion), while the
* observed HA and RA are related simply through the local
* apparent ST. "Observed" RA,Dec or HA,Dec thus means the
* position that would be seen by a perfect equatorial located
* at the observer and with its polar axis aligned to the
* Earth's axis of rotation (n.b. not to the refracted pole).
* By removing from the observed place the effects of
* atmospheric refraction and diurnal aberration, the
* geocentric apparent RA,Dec is obtained.
*
*  Frequently, mean rather than apparent RA,Dec will be required,
* in which case further transformations will be necessary. The
* palAmp etc routines will convert the apparent RA,Dec produced
* by the present routine into an "FK5" (J2000) mean place, by
* allowing for the Sun's gravitational lens effect, annual
* aberration, nutation and precession. Should "FK4" (1950)
* coordinates be needed, the routines palFk524 etc will also
* need to be applied.
*
*  To convert to apparent RA,Dec the coordinates read from a
* real telescope, corrections would have to be applied for
* encoder zero points, gear and encoder errors, tube flexure,
* the position of the rotator axis and the pointing axis
* relative to it, nonperpendicularity between the mounting
* axes, and finally for the tilt of the azimuth or polar axis
* of the mounting (with appropriate corrections for mount
* flexures). Some telescopes would, of course, exhibit other
* properties which would need to be accounted for at the
* appropriate point in the sequence.
*
*  This routine takes time to execute, due mainly to the rigorous
* integration used to evaluate the refraction. For processing
* multiple stars for one location and time, call palAoppa once
* followed by one call per star to palOapqk. Where a range of
* times within a limited period of a few hours is involved, and the
* highest precision is not required, call palAoppa once, followed
* by a call to palAoppat each time the time changes, followed by
* one call per star to palOapqk.
*
*  The DATE argument is UTC expressed as an MJD. This is, strictly
* speaking, wrong, because of leap seconds. However, as long as
* the delta UT and the UTC are consistent there are no
* difficulties, except during a leap second. In this case, the
* start of the 61st second of the final minute should begin a new
* MJD day and the old preleap delta UT should continue to be used.
* As the 61st second completes, the MJD should revert to the start
* of the day as, simultaneously, the delta UTC changes by one
* second to its postleap new value.
*
*  The delta UT (UT1UTC) is tabulated in IERS circulars and
* elsewhere. It increases by exactly one second at the end of
* each UTC leap second, introduced in order to keep delta UT
* within +/ 0.9 seconds.
*
*  IMPORTANT  TAKE CARE WITH THE LONGITUDE SIGN CONVENTION.
* The longitude required by the present routine is eastpositive,
* in accordance with geographical convention (and righthanded).
* In particular, note that the longitudes returned by the
* palOBS routine are westpositive, following astronomical
* usage, and must be reversed in sign before use in the present
* routine.
*
*  The polar coordinates XP,YP can be obtained from IERS
* circulars and equivalent publications. The maximum amplitude
* is about 0.3 arcseconds. If XP,YP values are unavailable,
* use XP=YP=0D0. See page B60 of the 1988 Astronomical Almanac
* for a definition of the two angles.
*
*  The height above sea level of the observing station, HM,
* can be obtained from the Astronomical Almanac (Section J
* in the 1988 edition), or via the routine palOBS. If P,
* the pressure in millibars, is available, an adequate
* estimate of HM can be obtained from the expression
*
* HM ~ 29.3*TSL*LOG(P/1013.25).
*
* where TSL is the approximate sealevel air temperature in K
* (see Astrophysical Quantities, C.W.Allen, 3rd edition,
* section 52). Similarly, if the pressure P is not known,
* it can be estimated from the height of the observing
* station, HM, as follows:
*
* P ~ 1013.25*EXP(HM/(29.3*TSL)).
*
* Note, however, that the refraction is nearly proportional to the
* pressure and that an accurate P value is important for precise
* work.
*
*  The azimuths etc. used by the present routine are with respect
* to the celestial pole. Corrections from the terrestrial pole
* can be computed using palPolmo.
* History:
* 20120827 (TIMJ):
* Initial version, copied from Fortran SLA
* Adapted with permission from the Fortran SLALIB library.
* {enter_further_changes_here}
* Copyright:
* Copyright (C) 2005 Patrick T. Wallace
* Copyright (C) 2012 Science and Technology Facilities Council.
* All Rights Reserved.
* Licence:
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 3 of
* the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be
* useful, but WITHOUT ANY WARRANTY; without even the implied
* warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
* PURPOSE. See the GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
* MA 021101301, USA.
* Bugs:
* {note_any_bugs_here}
*
*/
#include "pal.h"
void palOap ( const char *type, double ob1, double ob2, double date,
double dut, double elongm, double phim, double hm,
double xp, double yp, double tdk, double pmb,
double rh, double wl, double tlr,
double *rap, double *dap ) {
double aoprms[14];
palAoppa(date,dut,elongm,phim,hm,xp,yp,tdk,pmb,rh,wl,tlr,
aoprms);
palOapqk(type,ob1,ob2,aoprms,rap,dap);
}
