line |
stmt |
bran |
cond |
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pod |
time |
code |
1
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/* |
2
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*+ |
3
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* Name: |
4
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* palOap |
5
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6
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* Purpose: |
7
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* Observed to apparent place |
8
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9
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* Language: |
10
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* Starlink ANSI C |
11
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12
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* Type of Module: |
13
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* Library routine |
14
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15
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* Invocation: |
16
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* void palOap ( const char *type, double ob1, double ob2, double date, |
17
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* double dut, double elongm, double phim, double hm, |
18
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* double xp, double yp, double tdk, double pmb, |
19
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* double rh, double wl, double tlr, |
20
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* double *rap, double *dap ); |
21
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22
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* Arguments: |
23
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* type = const char * (Given) |
24
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* Type of coordinates - 'R', 'H' or 'A' (see below) |
25
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* ob1 = double (Given) |
26
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* Observed Az, HA or RA (radians; Az is N=0;E=90) |
27
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* ob2 = double (Given) |
28
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* Observed ZD or Dec (radians) |
29
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* date = double (Given) |
30
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* UTC date/time (Modified Julian Date, JD-2400000.5) |
31
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* dut = double (Given) |
32
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* delta UT: UT1-UTC (UTC seconds) |
33
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* elongm = double (Given) |
34
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* Mean longitude of the observer (radians, east +ve) |
35
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* phim = double (Given) |
36
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* Mean geodetic latitude of the observer (radians) |
37
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* hm = double (Given) |
38
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* Observer's height above sea level (metres) |
39
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* xp = double (Given) |
40
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* Polar motion x-coordinates (radians) |
41
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* yp = double (Given) |
42
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* Polar motion y-coordinates (radians) |
43
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* tdk = double (Given) |
44
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* Local ambient temperature (K; std=273.15) |
45
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* pmb = double (Given) |
46
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* Local atmospheric pressure (mb; std=1013.25) |
47
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* rh = double (Given) |
48
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* Local relative humidity (in the range 0.0-1.0) |
49
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* wl = double (Given) |
50
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* Effective wavelength (micron, e.g. 0.55) |
51
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* tlr = double (Given) |
52
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* Tropospheric laps rate (K/metre, e.g. 0.0065) |
53
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* rap = double * (Given) |
54
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* Geocentric apparent right ascension |
55
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* dap = double * (Given) |
56
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* Geocentric apparent declination |
57
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58
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* Description: |
59
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* Observed to apparent place. |
60
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61
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* Authors: |
62
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* PTW: Patrick T. Wallace |
63
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* TIMJ: Tim Jenness (JAC, Hawaii) |
64
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* {enter_new_authors_here} |
65
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66
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* Notes: |
67
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* - Only the first character of the TYPE argument is significant. |
68
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* 'R' or 'r' indicates that OBS1 and OBS2 are the observed right |
69
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* ascension and declination; 'H' or 'h' indicates that they are |
70
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* hour angle (west +ve) and declination; anything else ('A' or |
71
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* 'a' is recommended) indicates that OBS1 and OBS2 are azimuth |
72
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* (north zero, east 90 deg) and zenith distance. (Zenith |
73
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* distance is used rather than elevation in order to reflect the |
74
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* fact that no allowance is made for depression of the horizon.) |
75
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* |
76
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* - The accuracy of the result is limited by the corrections for |
77
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* refraction. Providing the meteorological parameters are |
78
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* known accurately and there are no gross local effects, the |
79
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* predicted apparent RA,Dec should be within about 0.1 arcsec |
80
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* for a zenith distance of less than 70 degrees. Even at a |
81
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* topocentric zenith distance of 90 degrees, the accuracy in |
82
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* elevation should be better than 1 arcmin; useful results |
83
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* are available for a further 3 degrees, beyond which the |
84
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* palRefro routine returns a fixed value of the refraction. |
85
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* The complementary routines palAop (or palAopqk) and palOap |
86
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* (or palOapqk) are self-consistent to better than 1 micro- |
87
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* arcsecond all over the celestial sphere. |
88
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* |
89
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* - It is advisable to take great care with units, as even |
90
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* unlikely values of the input parameters are accepted and |
91
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* processed in accordance with the models used. |
92
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* |
93
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* - "Observed" Az,El means the position that would be seen by a |
94
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* perfect theodolite located at the observer. This is |
95
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* related to the observed HA,Dec via the standard rotation, using |
96
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* the geodetic latitude (corrected for polar motion), while the |
97
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* observed HA and RA are related simply through the local |
98
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* apparent ST. "Observed" RA,Dec or HA,Dec thus means the |
99
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* position that would be seen by a perfect equatorial located |
100
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* at the observer and with its polar axis aligned to the |
101
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* Earth's axis of rotation (n.b. not to the refracted pole). |
102
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* By removing from the observed place the effects of |
103
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* atmospheric refraction and diurnal aberration, the |
104
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* geocentric apparent RA,Dec is obtained. |
105
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* |
106
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* - Frequently, mean rather than apparent RA,Dec will be required, |
107
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* in which case further transformations will be necessary. The |
108
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* palAmp etc routines will convert the apparent RA,Dec produced |
109
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* by the present routine into an "FK5" (J2000) mean place, by |
110
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* allowing for the Sun's gravitational lens effect, annual |
111
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* aberration, nutation and precession. Should "FK4" (1950) |
112
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* coordinates be needed, the routines palFk524 etc will also |
113
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* need to be applied. |
114
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* |
115
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* - To convert to apparent RA,Dec the coordinates read from a |
116
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* real telescope, corrections would have to be applied for |
117
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* encoder zero points, gear and encoder errors, tube flexure, |
118
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* the position of the rotator axis and the pointing axis |
119
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* relative to it, non-perpendicularity between the mounting |
120
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* axes, and finally for the tilt of the azimuth or polar axis |
121
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* of the mounting (with appropriate corrections for mount |
122
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* flexures). Some telescopes would, of course, exhibit other |
123
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* properties which would need to be accounted for at the |
124
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* appropriate point in the sequence. |
125
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* |
126
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* - This routine takes time to execute, due mainly to the rigorous |
127
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* integration used to evaluate the refraction. For processing |
128
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* multiple stars for one location and time, call palAoppa once |
129
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* followed by one call per star to palOapqk. Where a range of |
130
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* times within a limited period of a few hours is involved, and the |
131
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* highest precision is not required, call palAoppa once, followed |
132
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* by a call to palAoppat each time the time changes, followed by |
133
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* one call per star to palOapqk. |
134
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* |
135
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* - The DATE argument is UTC expressed as an MJD. This is, strictly |
136
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* speaking, wrong, because of leap seconds. However, as long as |
137
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* the delta UT and the UTC are consistent there are no |
138
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* difficulties, except during a leap second. In this case, the |
139
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* start of the 61st second of the final minute should begin a new |
140
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* MJD day and the old pre-leap delta UT should continue to be used. |
141
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* As the 61st second completes, the MJD should revert to the start |
142
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* of the day as, simultaneously, the delta UTC changes by one |
143
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* second to its post-leap new value. |
144
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* |
145
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* - The delta UT (UT1-UTC) is tabulated in IERS circulars and |
146
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* elsewhere. It increases by exactly one second at the end of |
147
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* each UTC leap second, introduced in order to keep delta UT |
148
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* within +/- 0.9 seconds. |
149
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* |
150
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* - IMPORTANT -- TAKE CARE WITH THE LONGITUDE SIGN CONVENTION. |
151
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* The longitude required by the present routine is east-positive, |
152
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* in accordance with geographical convention (and right-handed). |
153
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* In particular, note that the longitudes returned by the |
154
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* palOBS routine are west-positive, following astronomical |
155
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* usage, and must be reversed in sign before use in the present |
156
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* routine. |
157
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* |
158
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* - The polar coordinates XP,YP can be obtained from IERS |
159
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* circulars and equivalent publications. The maximum amplitude |
160
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* is about 0.3 arcseconds. If XP,YP values are unavailable, |
161
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* use XP=YP=0D0. See page B60 of the 1988 Astronomical Almanac |
162
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* for a definition of the two angles. |
163
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* |
164
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* - The height above sea level of the observing station, HM, |
165
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* can be obtained from the Astronomical Almanac (Section J |
166
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* in the 1988 edition), or via the routine palOBS. If P, |
167
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* the pressure in millibars, is available, an adequate |
168
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* estimate of HM can be obtained from the expression |
169
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* |
170
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* HM ~ -29.3*TSL*LOG(P/1013.25). |
171
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* |
172
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* where TSL is the approximate sea-level air temperature in K |
173
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* (see Astrophysical Quantities, C.W.Allen, 3rd edition, |
174
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* section 52). Similarly, if the pressure P is not known, |
175
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* it can be estimated from the height of the observing |
176
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* station, HM, as follows: |
177
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* |
178
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* P ~ 1013.25*EXP(-HM/(29.3*TSL)). |
179
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* |
180
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* Note, however, that the refraction is nearly proportional to the |
181
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* pressure and that an accurate P value is important for precise |
182
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* work. |
183
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* |
184
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* - The azimuths etc. used by the present routine are with respect |
185
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* to the celestial pole. Corrections from the terrestrial pole |
186
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* can be computed using palPolmo. |
187
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188
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* History: |
189
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* 2012-08-27 (TIMJ): |
190
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* Initial version, copied from Fortran SLA |
191
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* Adapted with permission from the Fortran SLALIB library. |
192
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* {enter_further_changes_here} |
193
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194
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* Copyright: |
195
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* Copyright (C) 2005 Patrick T. Wallace |
196
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* Copyright (C) 2012 Science and Technology Facilities Council. |
197
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* All Rights Reserved. |
198
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199
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* Licence: |
200
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* This program is free software; you can redistribute it and/or |
201
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* modify it under the terms of the GNU General Public License as |
202
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* published by the Free Software Foundation; either version 3 of |
203
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* the License, or (at your option) any later version. |
204
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* |
205
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* This program is distributed in the hope that it will be |
206
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* useful, but WITHOUT ANY WARRANTY; without even the implied |
207
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* warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR |
208
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* PURPOSE. See the GNU General Public License for more details. |
209
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* |
210
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* You should have received a copy of the GNU General Public License |
211
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* along with this program; if not, write to the Free Software |
212
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, |
213
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* MA 02110-1301, USA. |
214
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215
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* Bugs: |
216
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* {note_any_bugs_here} |
217
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*- |
218
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*/ |
219
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220
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#include "pal.h" |
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void palOap ( const char *type, double ob1, double ob2, double date, |
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double dut, double elongm, double phim, double hm, |
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double xp, double yp, double tdk, double pmb, |
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double rh, double wl, double tlr, |
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double *rap, double *dap ) { |
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double aoprms[14]; |
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palAoppa(date,dut,elongm,phim,hm,xp,yp,tdk,pmb,rh,wl,tlr, |
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aoprms); |
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palOapqk(type,ob1,ob2,aoprms,rap,dap); |
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} |