From fa080de7afc95aa1c19a6e6fc0e0708ced2eadc4 Mon Sep 17 00:00:00 2001
From: Joseph Hunkeler <jhunkeler@gmail.com>
Date: Wed, 8 Jul 2015 20:46:52 -0400
Subject: Initial commit

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+.help aopqk Jun99 "Slalib Package"
+.nf
+
+      SUBROUTINE slAOPQ (RAP, DAP, AOPRMS, AOB, ZOB, HOB, DOB, ROB)
+
+     - - - - - -
+      A O P Q
+     - - - - - -
+
+  Quick apparent to observed place (but see note 8, below, for
+  remarks about speed).
+
+  Given:
+     RAP    d      geocentric apparent right ascension
+     DAP    d      geocentric apparent declination
+     AOPRMS d(14)  star-independent apparent-to-observed parameters:
+
+       (1)      geodetic latitude (radians)
+       (2,3)    sine and cosine of geodetic latitude
+       (4)      magnitude of diurnal aberration vector
+       (5)      height (HM)
+       (6)      ambient temperature (T)
+       (7)      pressure (P)
+       (8)      relative humidity (RH)
+       (9)      wavelength (WL)
+       (10)     lapse rate (TLR)
+       (11,12)  refraction constants A and B (radians)
+       (13)     longitude + eqn of equinoxes + sidereal DUT (radians)
+       (14)     local apparent sidereal time (radians)
+
+  Returned:
+     AOB    d      observed azimuth (radians: N=0,E=90)
+     ZOB    d      observed zenith distance (radians)
+     HOB    d      observed Hour Angle (radians)
+     DOB    d      observed Declination (radians)
+     ROB    d      observed Right Ascension (radians)
+
+  Notes:
+
+   1)  This routine returns zenith distance rather than elevation
+       in order to reflect the fact that no allowance is made for
+       depression of the horizon.
+
+   2)  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
+       observed RA,Dec predicted by this routine 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 slaRefro routine returns a fixed value of the refraction.
+       The complementary routines slaAop (or slaAopqk) and slaOap
+       (or slaOapqk) are self-consistent to better than 1 micro-
+       arcsecond all over the celestial sphere.
+
+   3)  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.
+
+   4)  "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 slMAP 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
+       slFK45 etc routines.
+
+   5)  "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.
+
+   6)  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.
+
+   7)  The star-independent apparent-to-observed-place parameters
+       in AOPRMS may be computed by means of the slAOPA routine.
+       If nothing has changed significantly except the time, the
+       slAOPT routine may be used to perform the requisite
+       partial recomputation of AOPRMS.
+
+   8)  At zenith distances beyond about 76 degrees, the need for
+       special care with the corrections for refraction causes a
+       marked increase in execution time.  Moreover, the effect
+       gets worse with increasing zenith distance.  Adroit
+       programming in the calling application may allow the
+       problem to be reduced.  Prepare an alternative AOPRMS array,
+       computed for zero air-pressure;  this will disable the
+       refraction corrections and cause rapid execution.  Using
+       this AOPRMS array, a preliminary call to the present routine
+       will, depending on the application, produce a rough position
+       which may be enough to establish whether the full, slow
+       calculation (using the real AOPRMS array) is worthwhile.
+       For example, there would be no need for the full calculation
+       if the preliminary call had already established that the
+       source was well below the elevation limits for a particular
+       telescope.
+
+  9)   The azimuths etc produced by the present routine are with
+       respect to the celestial pole.  Corrections to the terrestrial
+       pole can be computed using slPLMO.
+
+  Called:  slDS2C, slREFZ, slRFRO, slDC2S, slDA2P
+
+  P.T.Wallace   Starlink   22 February 1996
+
+  Copyright (C) 1996 Rutherford Appleton Laboratory
+  Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.
+
+.fi
+.endhelp
-- 
cgit 

