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/*
*+
* Name:
* palAop
* Purpose:
* Apparent to observed place
* Language:
* Starlink ANSI C
* Type of Module:
* Library routine
* Invocation:
* void palAop ( double rap, double dap, 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 *aob, double *zob, double *hob,
* double *dob, double *rob );
* Arguments:
* rap = double (Given)
* Geocentric apparent right ascension
* dap = double (Given)
* Geocentirc apparent declination
* date = double (Given)
* UTC date/time (Modified Julian Date, JD-2400000.5)
* dut = double (Given)
* delta UT: UT1-UTC (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 x-coordinates (radians)
* yp = double (Given)
* Polar motion y-coordinates (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 0.0-1.0)
* wl = double (Given)
* Effective wavelength (micron, e.g. 0.55)
* tlr = double (Given)
* Tropospheric laps rate (K/metre, e.g. 0.0065)
* aob = double * (Returned)
* Observed azimuth (radians: N=0; E=90)
* zob = double * (Returned)
* Observed zenith distance (radians)
* hob = double * (Returned)
* Observed Hour Angle (radians)
* dob = double * (Returned)
* Observed Declination (radians)
* rob = double * (Returned)
* Observed Right Ascension (radians)
* Description:
* Apparent to observed place for sources distant from the solar system.
* Authors:
* PTW: Patrick T. Wallace
* TIMJ: Tim Jenness (JAC, Hawaii)
* {enter_new_authors_here}
* Notes:
* - This routine returns zenith distance 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 self-consistent 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.
*
* - "Apparent" place means the geocentric apparent right ascension
* and declination, which is obtained from a catalogue mean place
* by allowing for space motion, parallax, precession, nutation,
* annual aberration, and the Sun's gravitational lens effect. For
* star positions in the FK5 system (i.e. J2000), these effects can
* be applied by means of the palMap etc routines. Starting from
* other mean place systems, additional transformations will be
* needed; for example, FK4 (i.e. B1950) mean places would first
* have to be converted to FK5, which can be done with the
* palFk425 etc routines.
*
* - "Observed" Az,El means the position that would be seen by a
* perfect theodolite located at the observer. This is obtained
* from the geocentric apparent RA,Dec by allowing for Earth
* orientation and diurnal aberration, rotating from equator
* to horizon coordinates, and then adjusting for refraction.
* The HA,Dec is obtained by rotating back into equatorial
* coordinates, using the geodetic latitude corrected for polar
* motion, and is 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). Finally, the RA is obtained by subtracting
* the HA from the local apparent ST.
*
* - To predict the required setting of a real telescope, the
* observed place produced by this routine would have to be
* adjusted for the tilt of the azimuth or polar axis of the
* mounting (with appropriate corrections for mount flexures),
* for non-perpendicularity between the mounting axes, for the
* position of the rotator axis and the pointing axis relative
* to it, for tube flexure, for gear and encoder errors, and
* finally for encoder zero points. 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 palAopqk.
* 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 palAopqk.
*
* - 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 pre-leap 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 post-leap new value.
*
* - The delta UT (UT1-UTC) 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 east-positive,
* in accordance with geographical convention (and right-handed).
* In particular, note that the longitudes returned by the
* palObs routine are west-positive, 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=0.0. 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 sea-level 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 produced by the present routine are with
* respect to the celestial pole. Corrections to the terrestrial
* pole can be computed using palPolmo.
* History:
* 2012-08-25 (TIMJ):
* Initial version
* 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 02110-1301, USA.
* Bugs:
* {note_any_bugs_here}
*-
*/
#include "pal.h"
void palAop ( double rap, double dap, 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 *aob, double *zob, double *hob,
double *dob, double *rob ) {
double aoprms[14];
palAoppa(date,dut,elongm,phim,hm,xp,yp,tdk,pmb,rh,wl,tlr,
aoprms);
palAopqk(rap,dap,aoprms,aob,zob,hob,dob,rob);
}
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