1 ;;; lunar.el --- calendar functions for phases of the moon.
3 ;; Copyright (C) 1992, 1993 Free Software Foundation, Inc.
5 ;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
7 ;; Human-Keywords: moon, lunar phases, calendar, diary
9 ;; This file is part of GNU Emacs.
11 ;; GNU Emacs is distributed in the hope that it will be useful,
12 ;; but WITHOUT ANY WARRANTY. No author or distributor
13 ;; accepts responsibility to anyone for the consequences of using it
14 ;; or for whether it serves any particular purpose or works at all,
15 ;; unless he says so in writing. Refer to the GNU Emacs General Public
16 ;; License for full details.
18 ;; Everyone is granted permission to copy, modify and redistribute
19 ;; GNU Emacs, but only under the conditions described in the
20 ;; GNU Emacs General Public License. A copy of this license is
21 ;; supposed to have been given to you along with GNU Emacs so you
22 ;; can know your rights and responsibilities. It should be in a
23 ;; file named COPYING. Among other things, the copyright notice
24 ;; and this notice must be preserved on all copies.
28 ;; This collection of functions implements lunar phases for calendar.el and
31 ;; Based on ``Astronomical Formulae for Calculators,'' 3rd ed., by Jean Meeus,
32 ;; Willmann-Bell, Inc., 1985.
34 ;; WARNING: The calculations will be accurate only to within a few minutes.
36 ;; The author would be delighted to have an astronomically more sophisticated
37 ;; person rewrite the code for the lunar calculations in this file!
39 ;; Comments, corrections, and improvements should be sent to
40 ;; Edward M. Reingold Department of Computer Science
41 ;; (217) 333-6733 University of Illinois at Urbana-Champaign
42 ;; reingold@cs.uiuc.edu 1304 West Springfield Avenue
43 ;; Urbana, Illinois 61801
48 (require 'lisp-float-type
)
49 (error "Lunar calculations impossible since floating point is unavailable."))
53 (defun lunar-phase-list (month year
)
54 "List of lunar phases for three months starting with Gregorian MONTH, YEAR."
55 (let ((end-month month
)
59 (increment-calendar-month end-month end-year
3)
60 (increment-calendar-month start-month start-year -
1)
61 (let* ((end-date (list (list end-month
1 end-year
)))
62 (start-date (list (list start-month
63 (calendar-last-day-of-month
64 start-month start-year
)
70 ( / (calendar-day-number (list month
1 year
))
73 (new-moon (lunar-phase index
))
75 (while (calendar-date-compare new-moon end-date
)
76 (if (calendar-date-compare start-date new-moon
)
77 (setq list
(append list
(list new-moon
))))
78 (setq index
(1+ index
))
79 (setq new-moon
(lunar-phase index
)))
82 (defun lunar-phase (index)
83 "Local date and time of lunar phase INDEX.
84 Integer below INDEX/4 gives the lunation number, counting from Jan 1, 1900;
85 remainder mod 4 gives the phase: 0 new moon, 1 first quarter, 2 full moon,
87 (let* ((phase (calendar-mod index
4))
89 (time (/ index
1236.85))
90 (date (+ (calendar-absolute-from-gregorian '(1 0.5 1900))
93 (* 0.0001178 time time
)
94 (* -
0.000000155 time time time
)
96 (solar-sin-degrees (+ 166.56
98 (* -
0.009173 time time
))))))
102 (* -
0.0000333 time time
)
103 (* -
0.00000347 time time time
))
107 (* 385.81691806 index
)
108 (* 0.0107306 time time
)
109 (* 0.00001236 time time time
))
113 (* 390.67050646 index
)
114 (* -
0.0016528 time time
)
115 (* -
0.00000239 time time time
))
118 (if (memq phase
'(0 2))
119 (+ (* (- 0.1734 (* 0.000393 time
))
120 (solar-sin-degrees sun-anomaly
))
121 (* 0.0021 (solar-sin-degrees (* 2 sun-anomaly
)))
122 (* -
0.4068 (solar-sin-degrees moon-anomaly
))
123 (* 0.0161 (solar-sin-degrees (* 2 moon-anomaly
)))
124 (* -
0.0004 (solar-sin-degrees (* 3 moon-anomaly
)))
125 (* 0.0104 (solar-sin-degrees (* 2 moon-lat
)))
126 (* -
0.0051 (solar-sin-degrees (+ sun-anomaly moon-anomaly
)))
127 (* -
0.0074 (solar-sin-degrees (- sun-anomaly moon-anomaly
)))
128 (* 0.0004 (solar-sin-degrees (+ (* 2 moon-lat
) sun-anomaly
)))
129 (* -
0.0004 (solar-sin-degrees (- (* 2 moon-lat
) sun-anomaly
)))
130 (* -
0.0006 (solar-sin-degrees
131 (+ (* 2 moon-lat
) moon-anomaly
)))
132 (* 0.0010 (solar-sin-degrees (- (* 2 moon-lat
) moon-anomaly
)))
133 (* 0.0005 (solar-sin-degrees
134 (+ (* 2 moon-anomaly
) sun-anomaly
))))
135 (+ (* (- 0.1721 (* 0.0004 time
))
136 (solar-sin-degrees sun-anomaly
))
137 (* 0.0021 (solar-sin-degrees (* 2 sun-anomaly
)))
138 (* -
0.6280 (solar-sin-degrees moon-anomaly
))
139 (* 0.0089 (solar-sin-degrees (* 2 moon-anomaly
)))
140 (* -
0.0004 (solar-sin-degrees (* 3 moon-anomaly
)))
141 (* 0.0079 (solar-sin-degrees (* 2 moon-lat
)))
142 (* -
0.0119 (solar-sin-degrees (+ sun-anomaly moon-anomaly
)))
143 (* -
0.0047 (solar-sin-degrees (- sun-anomaly moon-anomaly
)))
144 (* 0.0003 (solar-sin-degrees (+ (* 2 moon-lat
) sun-anomaly
)))
145 (* -
0.0004 (solar-sin-degrees (- (* 2 moon-lat
) sun-anomaly
)))
146 (* -
0.0006 (solar-sin-degrees (+ (* 2 moon-lat
) moon-anomaly
)))
147 (* 0.0021 (solar-sin-degrees (- (* 2 moon-lat
) moon-anomaly
)))
148 (* 0.0003 (solar-sin-degrees
149 (+ (* 2 moon-anomaly
) sun-anomaly
)))
150 (* 0.0004 (solar-sin-degrees
151 (- sun-anomaly
(* 2 moon-anomaly
))))
152 (* -
0.0003 (solar-sin-degrees
153 (+ (* 2 sun-anomaly
) moon-anomaly
))))))
155 (* -
0.0004 (solar-cosine-degrees
157 (* 0.0003 (solar-cosine-degrees
159 (adjustment (cond ((= phase
1) (+ adjustment adj
))
160 ((= phase
2) (- adjustment adj
))
162 (date (+ date adjustment
))
163 (date (+ date
(/ (- calendar-time-zone
164 (solar-ephemeris-correction
165 (extract-calendar-year
166 (calendar-gregorian-from-absolute
169 (time (* 24 (- date
(truncate date
))))
170 (date (calendar-gregorian-from-absolute (truncate date
))))
171 (list date
(solar-time-string time date
) phase
)))
173 (defun lunar-phase-name (phase)
174 "Name of lunar PHASE.
175 0 = new moon, 1 = first quarter, 2 = full moon, 3 = last quarter."
176 (cond ((= 0 phase
) "New Moon")
177 ((= 1 phase
) "First Quarter Moon")
178 ((= 2 phase
) "Full Moon")
179 ((= 3 phase
) "Last Quarter Moon")))
181 (defun calendar-phases-of-moon ()
182 "Create a buffer with the lunar phases for the current calendar window."
184 (message "Computing phases of the moon...")
185 (let ((m1 displayed-month
)
189 (lunar-phases-buffer "*Phases of Moon*"))
190 (increment-calendar-month m1 y1 -
1)
191 (increment-calendar-month m2 y2
1)
192 (set-buffer (get-buffer-create lunar-phases-buffer
))
193 (setq buffer-read-only nil
)
194 (calendar-set-mode-line
196 (format "Phases of the Moon from %s to %s, %d%%-"
197 (calendar-month-name m1
) (calendar-month-name m2
) y2
)
198 (format "Phases of the Moon from %s, %d to %s, %d%%-"
199 (calendar-month-name m1
) y1
(calendar-month-name m2
) y2
)))
206 (phase (car (cdr (cdr x
)))))
207 (concat (calendar-date-string date
)
209 (lunar-phase-name phase
)
212 (lunar-phase-list m1 y1
) "\n"))
213 (goto-char (point-min))
214 (set-buffer-modified-p nil
)
215 (setq buffer-read-only t
)
216 (display-buffer lunar-phases-buffer
)
217 (message "Computing phases of the moon...done")))
220 (defun phases-of-moon (&optional arg
)
221 "Display the quarters of the moon for last month, this month, and next month.
222 If called with an optional prefix argument, prompts for month and year.
224 This function is suitable for execution in a .emacs file."
227 (let* ((completion-ignore-case t
)
228 (date (calendar-current-date))
235 (mapcar 'list
(append calendar-month-name-array nil
))
237 (calendar-make-alist calendar-month-name-array
)))
238 (extract-calendar-month date
)))
243 '(lambda (x) (> x
0))
245 (extract-calendar-year (calendar-current-date))))
246 (extract-calendar-year date
))))
247 (calendar-phases-of-moon))))
249 (defun diary-phases-of-moon ()
250 "Moon phases diary entry."
254 (+ (extract-calendar-year date
)
255 ( / (calendar-day-number date
)
258 (phase (lunar-phase index
)))
259 (while (calendar-date-compare phase
(list date
))
260 (setq index
(1+ index
))
261 (setq phase
(lunar-phase index
)))
262 (if (calendar-date-equal (car phase
) date
)
263 (concat (lunar-phase-name (car (cdr (cdr phase
)))) " "
264 (car (cdr phase
))))))
268 ;;; lunar.el ends here