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authorJoe Hunkeler <jhunkeler@gmail.com>2015-08-11 16:51:37 -0400
committerJoe Hunkeler <jhunkeler@gmail.com>2015-08-11 16:51:37 -0400
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+.help altaz Jun99 "Slalib Package"
+.nf
+
+ SUBROUTINE slALAZ (HA, DEC, PHI,
+ : AZ, AZD, AZDD, EL, ELD, ELDD, PA, PAD, PADD)
+
+ - - - - - -
+ A L A Z
+ - - - - - -
+
+ Positions, velocities and accelerations for an altazimuth
+ telescope mount.
+
+ (double precision)
+
+ Given:
+ HA d hour angle
+ DEC d declination
+ PHI d observatory latitude
+
+ Returned:
+ AZ d azimuth
+ AZD d " velocity
+ AZDD d " acceleration
+ EL d elevation
+ ELD d " velocity
+ ELDD d " acceleration
+ PA d parallactic angle
+ PAD d " " velocity
+ PADD d " " acceleration
+
+ Notes:
+
+ 1) Natural units are used throughout. HA, DEC, PHI, AZ, EL
+ and ZD are in radians. The velocities and accelerations
+ assume constant declination and constant rate of change of
+ hour angle (as for tracking a star); the units of AZD, ELD
+ and PAD are radians per radian of HA, while the units of AZDD,
+ ELDD and PADD are radians per radian of HA squared. To
+ convert into practical degree- and second-based units:
+
+ angles * 360/2pi -> degrees
+ velocities * (2pi/86400)*(360/2pi) -> degree/sec
+ accelerations * ((2pi/86400)**2)*(360/2pi) -> degree/sec/sec
+
+ Note that the seconds here are sidereal rather than SI. One
+ sidereal second is about 0.99727 SI seconds.
+
+ The velocity and acceleration factors assume the sidereal
+ tracking case. Their respective numerical values are (exactly)
+ 1/240 and (approximately) 1/3300236.9.
+
+ 2) Azimuth is returned in the range 0-2pi; north is zero,
+ and east is +pi/2. Elevation and parallactic angle are
+ returned in the range +/-pi/2. Position angle is +ve
+ for a star west of the meridian and is the angle NP-star-zenith.
+
+ 3) The latitude is geodetic as opposed to geocentric. The
+ hour angle and declination are topocentric. Refraction and
+ deficiencies in the telescope mounting are ignored. The
+ purpose of the routine is to give the general form of the
+ quantities. The details of a real telescope could profoundly
+ change the results, especially close to the zenith.
+
+ 4) No range checking of arguments is carried out.
+
+ 5) In applications which involve many such calculations, rather
+ than calling the present routine it will be more efficient to
+ use inline code, having previously computed fixed terms such
+ as sine and cosine of latitude, and (for tracking a star)
+ sine and cosine of declination.
+
+ P.T.Wallace Starlink 14 March 1997
+
+ Copyright (C) 1997 Rutherford Appleton Laboratory
+ Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.
+
+.fi
+.endhelp