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[emacs.git] / lisp / calendar / lunar.el
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1 ;;; lunar.el --- calendar functions for phases of the moon
3 ;; Copyright (C) 1992, 1993, 1995, 1997, 2001, 2002, 2003, 2004, 2005,
4 ;; 2006, 2007, 2008 Free Software Foundation, Inc.
6 ;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
7 ;; Maintainer: Glenn Morris <rgm@gnu.org>
8 ;; Keywords: calendar
9 ;; Human-Keywords: moon, lunar phases, calendar, diary
11 ;; This file is part of GNU Emacs.
13 ;; GNU Emacs is free software; you can redistribute it and/or modify
14 ;; it under the terms of the GNU General Public License as published by
15 ;; the Free Software Foundation; either version 3, or (at your option)
16 ;; any later version.
18 ;; GNU Emacs is distributed in the hope that it will be useful,
19 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
20 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
21 ;; GNU General Public License for more details.
23 ;; You should have received a copy of the GNU General Public License
24 ;; along with GNU Emacs; see the file COPYING. If not, write to the
25 ;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
26 ;; Boston, MA 02110-1301, USA.
28 ;;; Commentary:
30 ;; This collection of functions implements lunar phases for calendar.el and
31 ;; diary.el.
33 ;; Based on ``Astronomical Formulae for Calculators,'' 3rd ed., by Jean Meeus,
34 ;; Willmann-Bell, Inc., 1985 and ``Astronomical Algorithms'' by Jean Meeus,
35 ;; Willmann-Bell, Inc., 1991.
37 ;; WARNING: The calculations will be accurate only to within a few minutes.
39 ;; The author would be delighted to have an astronomically more sophisticated
40 ;; person rewrite the code for the lunar calculations in this file!
42 ;; Technical details of all the calendrical calculations can be found in
43 ;; ``Calendrical Calculations: The Millennium Edition'' by Edward M. Reingold
44 ;; and Nachum Dershowitz, Cambridge University Press (2001).
46 ;;; Code:
48 (if (fboundp 'atan)
49 (require 'lisp-float-type)
50 (error "Lunar calculations impossible since floating point is unavailable"))
52 (require 'solar)
54 (defun lunar-phase (index)
55 "Local date and time of lunar phase INDEX.
56 Integer below INDEX/4 gives the lunation number, counting from Jan 1, 1900;
57 remainder mod 4 gives the phase: 0 new moon, 1 first quarter, 2 full moon,
58 3 last quarter."
59 (let* ((phase (mod index 4))
60 (index (/ index 4.0))
61 (time (/ index 1236.85))
62 (date (+ (calendar-absolute-from-gregorian '(1 0.5 1900))
63 0.75933
64 (* 29.53058868 index)
65 (* 0.0001178 time time)
66 (* -0.000000155 time time time)
67 (* 0.00033
68 (solar-sin-degrees (+ 166.56
69 (* 132.87 time)
70 (* -0.009173 time time))))))
71 (sun-anomaly (mod
72 (+ 359.2242
73 (* 29.105356 index)
74 (* -0.0000333 time time)
75 (* -0.00000347 time time time))
76 360.0))
77 (moon-anomaly (mod
78 (+ 306.0253
79 (* 385.81691806 index)
80 (* 0.0107306 time time)
81 (* 0.00001236 time time time))
82 360.0))
83 (moon-lat (mod
84 (+ 21.2964
85 (* 390.67050646 index)
86 (* -0.0016528 time time)
87 (* -0.00000239 time time time))
88 360.0))
89 (adjustment
90 (if (memq phase '(0 2))
91 (+ (* (- 0.1734 (* 0.000393 time))
92 (solar-sin-degrees sun-anomaly))
93 (* 0.0021 (solar-sin-degrees (* 2 sun-anomaly)))
94 (* -0.4068 (solar-sin-degrees moon-anomaly))
95 (* 0.0161 (solar-sin-degrees (* 2 moon-anomaly)))
96 (* -0.0004 (solar-sin-degrees (* 3 moon-anomaly)))
97 (* 0.0104 (solar-sin-degrees (* 2 moon-lat)))
98 (* -0.0051 (solar-sin-degrees (+ sun-anomaly moon-anomaly)))
99 (* -0.0074 (solar-sin-degrees (- sun-anomaly moon-anomaly)))
100 (* 0.0004 (solar-sin-degrees (+ (* 2 moon-lat) sun-anomaly)))
101 (* -0.0004 (solar-sin-degrees (- (* 2 moon-lat) sun-anomaly)))
102 (* -0.0006 (solar-sin-degrees
103 (+ (* 2 moon-lat) moon-anomaly)))
104 (* 0.0010 (solar-sin-degrees (- (* 2 moon-lat) moon-anomaly)))
105 (* 0.0005 (solar-sin-degrees
106 (+ (* 2 moon-anomaly) sun-anomaly))))
107 (+ (* (- 0.1721 (* 0.0004 time))
108 (solar-sin-degrees sun-anomaly))
109 (* 0.0021 (solar-sin-degrees (* 2 sun-anomaly)))
110 (* -0.6280 (solar-sin-degrees moon-anomaly))
111 (* 0.0089 (solar-sin-degrees (* 2 moon-anomaly)))
112 (* -0.0004 (solar-sin-degrees (* 3 moon-anomaly)))
113 (* 0.0079 (solar-sin-degrees (* 2 moon-lat)))
114 (* -0.0119 (solar-sin-degrees (+ sun-anomaly moon-anomaly)))
115 (* -0.0047 (solar-sin-degrees (- sun-anomaly moon-anomaly)))
116 (* 0.0003 (solar-sin-degrees (+ (* 2 moon-lat) sun-anomaly)))
117 (* -0.0004 (solar-sin-degrees (- (* 2 moon-lat) sun-anomaly)))
118 (* -0.0006 (solar-sin-degrees (+ (* 2 moon-lat) moon-anomaly)))
119 (* 0.0021 (solar-sin-degrees (- (* 2 moon-lat) moon-anomaly)))
120 (* 0.0003 (solar-sin-degrees
121 (+ (* 2 moon-anomaly) sun-anomaly)))
122 (* 0.0004 (solar-sin-degrees
123 (- sun-anomaly (* 2 moon-anomaly))))
124 (* -0.0003 (solar-sin-degrees
125 (+ (* 2 sun-anomaly) moon-anomaly))))))
126 (adj (+ 0.0028
127 (* -0.0004 (solar-cosine-degrees
128 sun-anomaly))
129 (* 0.0003 (solar-cosine-degrees
130 moon-anomaly))))
131 (adjustment (cond ((= phase 1) (+ adjustment adj))
132 ((= phase 2) (- adjustment adj))
133 (t adjustment)))
134 (date (+ date adjustment))
135 (date (+ date (/ (- calendar-time-zone
136 (solar-ephemeris-correction
137 (extract-calendar-year
138 (calendar-gregorian-from-absolute
139 (truncate date)))))
140 60.0 24.0)))
141 (time (* 24 (- date (truncate date))))
142 (date (calendar-gregorian-from-absolute (truncate date)))
143 (adj (dst-adjust-time date time)))
144 (list (car adj) (apply 'solar-time-string (cdr adj)) phase)))
146 (defun lunar-phase-list (month year)
147 "List of lunar phases for three months starting with Gregorian MONTH, YEAR."
148 (let ((end-month month)
149 (end-year year)
150 (start-month month)
151 (start-year year))
152 (increment-calendar-month end-month end-year 3)
153 (increment-calendar-month start-month start-year -1)
154 (let* ((end-date (list (list end-month 1 end-year)))
155 (start-date (list (list start-month
156 (calendar-last-day-of-month
157 start-month start-year)
158 start-year)))
159 (index (* 4
160 (truncate
161 (* 12.3685
162 (+ year
163 ( / (calendar-day-number (list month 1 year))
164 366.0)
165 -1900)))))
166 (new-moon (lunar-phase index))
167 (list))
168 (while (calendar-date-compare new-moon end-date)
169 (if (calendar-date-compare start-date new-moon)
170 (setq list (append list (list new-moon))))
171 (setq index (1+ index)
172 new-moon (lunar-phase index)))
173 list)))
175 (defun lunar-phase-name (phase)
176 "Name of lunar PHASE.
177 0 = new moon, 1 = first quarter, 2 = full moon, 3 = last quarter."
178 (cond ((= 0 phase) "New Moon")
179 ((= 1 phase) "First Quarter Moon")
180 ((= 2 phase) "Full Moon")
181 ((= 3 phase) "Last Quarter Moon")))
183 (defvar displayed-month) ; from generate-calendar
184 (defvar displayed-year)
186 ;;;###cal-autoload
187 (defun calendar-phases-of-moon ()
188 "Create a buffer with the lunar phases for the current calendar window."
189 (interactive)
190 (message "Computing phases of the moon...")
191 (let ((m1 displayed-month)
192 (y1 displayed-year)
193 (m2 displayed-month)
194 (y2 displayed-year))
195 (increment-calendar-month m1 y1 -1)
196 (increment-calendar-month m2 y2 1)
197 (set-buffer (get-buffer-create lunar-phases-buffer))
198 (setq buffer-read-only nil)
199 (calendar-set-mode-line
200 (if (= y1 y2)
201 (format "Phases of the Moon from %s to %s, %d%%-"
202 (calendar-month-name m1) (calendar-month-name m2) y2)
203 (format "Phases of the Moon from %s, %d to %s, %d%%-"
204 (calendar-month-name m1) y1 (calendar-month-name m2) y2)))
205 (erase-buffer)
206 (insert
207 (mapconcat
208 (lambda (x)
209 (let ((date (car x))
210 (time (cadr x))
211 (phase (nth 2 x)))
212 (concat (calendar-date-string date)
213 ": "
214 (lunar-phase-name phase)
216 time)))
217 (lunar-phase-list m1 y1) "\n"))
218 (goto-char (point-min))
219 (set-buffer-modified-p nil)
220 (setq buffer-read-only t)
221 (display-buffer lunar-phases-buffer)
222 (message "Computing phases of the moon...done")))
224 ;;;###autoload
225 (defun phases-of-moon (&optional arg)
226 "Display the quarters of the moon for last month, this month, and next month.
227 If called with an optional prefix argument ARG, prompts for month and year.
228 This function is suitable for execution in a .emacs file."
229 (interactive "P")
230 (save-excursion
231 (let* ((date (if arg (calendar-read-date t)
232 (calendar-current-date)))
233 (displayed-month (extract-calendar-month date))
234 (displayed-year (extract-calendar-year date)))
235 (calendar-phases-of-moon))))
237 (defvar date)
239 ;; To be called from list-sexp-diary-entries, where DATE is bound.
241 ;;;###diary-autoload
242 (defun diary-phases-of-moon (&optional mark)
243 "Moon phases diary entry.
244 An optional parameter MARK specifies a face or single-character string to
245 use when highlighting the day in the calendar."
246 (let* ((index (* 4
247 (truncate
248 (* 12.3685
249 (+ (extract-calendar-year date)
250 ( / (calendar-day-number date)
251 366.0)
252 -1900)))))
253 (phase (lunar-phase index)))
254 (while (calendar-date-compare phase (list date))
255 (setq index (1+ index)
256 phase (lunar-phase index)))
257 (if (calendar-date-equal (car phase) date)
258 (cons mark (concat (lunar-phase-name (nth 2 phase)) " "
259 (cadr phase))))))
261 ;; For the Chinese calendar the calculations for the new moon need to be more
262 ;; accurate than those above, so we use more terms in the approximation.
263 (defun lunar-new-moon-time (k)
264 "Astronomical (Julian) day number of K th new moon."
265 (let* ((T (/ k 1236.85))
266 (T2 (* T T))
267 (T3 (* T T T))
268 (T4 (* T2 T2))
269 (JDE (+ 2451550.09765
270 (* 29.530588853 k)
271 (* 0.0001337 T2)
272 (* -0.000000150 T3)
273 (* 0.00000000073 T4)))
274 (E (- 1 (* 0.002516 T) (* 0.0000074 T2)))
275 (sun-anomaly (+ 2.5534
276 (* 29.10535669 k)
277 (* -0.0000218 T2)
278 (* -0.00000011 T3)))
279 (moon-anomaly (+ 201.5643
280 (* 385.81693528 k)
281 (* 0.0107438 T2)
282 (* 0.00001239 T3)
283 (* -0.000000058 T4)))
284 (moon-argument (+ 160.7108
285 (* 390.67050274 k)
286 (* -0.0016341 T2)
287 (* -0.00000227 T3)
288 (* 0.000000011 T4)))
289 (omega (+ 124.7746
290 (* -1.56375580 k)
291 (* 0.0020691 T2)
292 (* 0.00000215 T3)))
293 (A1 (+ 299.77 (* 0.107408 k) (* -0.009173 T2)))
294 (A2 (+ 251.88 (* 0.016321 k)))
295 (A3 (+ 251.83 (* 26.641886 k)))
296 (A4 (+ 349.42 (* 36.412478 k)))
297 (A5 (+ 84.66 (* 18.206239 k)))
298 (A6 (+ 141.74 (* 53.303771 k)))
299 (A7 (+ 207.14 (* 2.453732 k)))
300 (A8 (+ 154.84 (* 7.306860 k)))
301 (A9 (+ 34.52 (* 27.261239 k)))
302 (A10 (+ 207.19 (* 0.121824 k)))
303 (A11 (+ 291.34 (* 1.844379 k)))
304 (A12 (+ 161.72 (* 24.198154 k)))
305 (A13 (+ 239.56 (* 25.513099 k)))
306 (A14 (+ 331.55 (* 3.592518 k)))
307 (correction
308 (+ (* -0.40720 (solar-sin-degrees moon-anomaly))
309 (* 0.17241 E (solar-sin-degrees sun-anomaly))
310 (* 0.01608 (solar-sin-degrees (* 2 moon-anomaly)))
311 (* 0.01039 (solar-sin-degrees (* 2 moon-argument)))
312 (* 0.00739 E (solar-sin-degrees (- moon-anomaly sun-anomaly)))
313 (* -0.00514 E (solar-sin-degrees (+ moon-anomaly sun-anomaly)))
314 (* 0.00208 E E (solar-sin-degrees (* 2 sun-anomaly)))
315 (* -0.00111 (solar-sin-degrees
316 (- moon-anomaly (* 2 moon-argument))))
317 (* -0.00057 (solar-sin-degrees
318 (+ moon-anomaly (* 2 moon-argument))))
319 (* 0.00056 E (solar-sin-degrees
320 (+ (* 2 moon-anomaly) sun-anomaly)))
321 (* -0.00042 (solar-sin-degrees (* 3 moon-anomaly)))
322 (* 0.00042 E (solar-sin-degrees
323 (+ sun-anomaly (* 2 moon-argument))))
324 (* 0.00038 E (solar-sin-degrees
325 (- sun-anomaly (* 2 moon-argument))))
326 (* -0.00024 E (solar-sin-degrees
327 (- (* 2 moon-anomaly) sun-anomaly)))
328 (* -0.00017 (solar-sin-degrees omega))
329 (* -0.00007 (solar-sin-degrees
330 (+ moon-anomaly (* 2 sun-anomaly))))
331 (* 0.00004 (solar-sin-degrees
332 (- (* 2 moon-anomaly) (* 2 moon-argument))))
333 (* 0.00004 (solar-sin-degrees (* 3 sun-anomaly)))
334 (* 0.00003 (solar-sin-degrees (+ moon-anomaly sun-anomaly
335 (* -2 moon-argument))))
336 (* 0.00003 (solar-sin-degrees
337 (+ (* 2 moon-anomaly) (* 2 moon-argument))))
338 (* -0.00003 (solar-sin-degrees (+ moon-anomaly sun-anomaly
339 (* 2 moon-argument))))
340 (* 0.00003 (solar-sin-degrees (- moon-anomaly sun-anomaly
341 (* -2 moon-argument))))
342 (* -0.00002 (solar-sin-degrees (- moon-anomaly sun-anomaly
343 (* 2 moon-argument))))
344 (* -0.00002 (solar-sin-degrees
345 (+ (* 3 moon-anomaly) sun-anomaly)))
346 (* 0.00002 (solar-sin-degrees (* 4 moon-anomaly)))))
347 (additional
348 (+ (* 0.000325 (solar-sin-degrees A1))
349 (* 0.000165 (solar-sin-degrees A2))
350 (* 0.000164 (solar-sin-degrees A3))
351 (* 0.000126 (solar-sin-degrees A4))
352 (* 0.000110 (solar-sin-degrees A5))
353 (* 0.000062 (solar-sin-degrees A6))
354 (* 0.000060 (solar-sin-degrees A7))
355 (* 0.000056 (solar-sin-degrees A8))
356 (* 0.000047 (solar-sin-degrees A9))
357 (* 0.000042 (solar-sin-degrees A10))
358 (* 0.000040 (solar-sin-degrees A11))
359 (* 0.000037 (solar-sin-degrees A12))
360 (* 0.000035 (solar-sin-degrees A13))
361 (* 0.000023 (solar-sin-degrees A14))))
362 (newJDE (+ JDE correction additional)))
363 (+ newJDE
364 (- (solar-ephemeris-correction
365 (extract-calendar-year
366 (calendar-gregorian-from-absolute
367 (floor (calendar-absolute-from-astro newJDE))))))
368 (/ calendar-time-zone 60.0 24.0))))
370 (defun lunar-new-moon-on-or-after (d)
371 "Julian day number of first new moon on or after Julian day number D.
372 The fractional part is the time of day.
374 The date and time are local time, including any daylight saving rules,
375 as governed by the values of `calendar-daylight-savings-starts',
376 `calendar-daylight-savings-starts-time', `calendar-daylight-savings-ends',
377 `calendar-daylight-savings-ends-time', `calendar-daylight-time-offset', and
378 `calendar-time-zone'."
379 (let* ((date (calendar-gregorian-from-absolute
380 (floor (calendar-absolute-from-astro d))))
381 (year (+ (extract-calendar-year date)
382 (/ (calendar-day-number date) 365.25)))
383 (k (floor (* (- year 2000.0) 12.3685)))
384 (date (lunar-new-moon-time k)))
385 (while (< date d)
386 (setq k (1+ k)
387 date (lunar-new-moon-time k)))
388 (let* ((a-date (calendar-absolute-from-astro date))
389 (time (* 24 (- a-date (truncate a-date))))
390 (date (calendar-gregorian-from-absolute (truncate a-date)))
391 (adj (dst-adjust-time date time)))
392 (calendar-astro-from-absolute
393 (+ (calendar-absolute-from-gregorian (car adj))
394 (/ (cadr adj) 24.0))))))
396 (provide 'lunar)
398 ;; arch-tag: 72f0b8a4-7bcc-4a1b-b67a-ff53c4a1d222
399 ;;; lunar.el ends here