[bpt/emacs.git] / lisp / calendar / lunar.el

;;; lunar.el --- calendar functions for phases of the moon.

;; Copyright (C) 1992, 1993, 1995, 1997 Free Software Foundation, Inc.

;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
;; Keywords: calendar
;; Human-Keywords: moon, lunar phases, calendar, diary

;; This file is part of GNU Emacs.

;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;;; Commentary:

;; This collection of functions implements lunar phases for calendar.el and
;; diary.el.

;; Based on ``Astronomical Formulae for Calculators,'' 3rd ed., by Jean Meeus,
;; Willmann-Bell, Inc., 1985 and ``Astronomical Algorithms'' by Jean Meeus,
;; Willmann-Bell, Inc., 1991.
;;
;; WARNING: The calculations will be accurate only to within a few minutes.

;; The author would be delighted to have an astronomically more sophisticated
;; person rewrite the code for the lunar calculations in this file!

;; Technical details of all the calendrical calculations can be found in
;; ``Calendrical Calculations'' by Nachum Dershowitz and Edward M. Reingold,
;; Cambridge University Press (1997).

;; Comments, corrections, and improvements should be sent to
;;  Edward M. Reingold               Department of Computer Science
;;  (217) 333-6733                   University of Illinois at Urbana-Champaign
;;  reingold@cs.uiuc.edu             1304 West Springfield Avenue
;;                                   Urbana, Illinois 61801

;;; Code:

(if (fboundp 'atan)
    (require 'lisp-float-type)
  (error "Lunar calculations impossible since floating point is unavailable."))

(require 'solar)

(defun lunar-phase-list (month year)
  "List of lunar phases for three months starting with Gregorian MONTH, YEAR."
  (let ((end-month month)
        (end-year year)
        (start-month month)
        (start-year year))
    (increment-calendar-month end-month end-year 3)
    (increment-calendar-month start-month start-year -1)
    (let* ((end-date (list (list end-month 1 end-year)))
           (start-date (list (list start-month 
                                   (calendar-last-day-of-month
                                    start-month start-year)
                                   start-year)))
           (index (* 4
                     (truncate
                      (* 12.3685
                         (+ year
                            ( / (calendar-day-number (list month 1 year))
                                366.0)
                            -1900)))))
           (new-moon (lunar-phase index))
           (list))
      (while (calendar-date-compare new-moon end-date)
        (if (calendar-date-compare start-date new-moon)
            (setq list (append list (list new-moon))))
        (setq index (1+ index))
        (setq new-moon (lunar-phase index)))
      list)))

(defun lunar-phase (index)
  "Local date and time of lunar phase INDEX.
Integer below INDEX/4 gives the lunation number, counting from Jan 1, 1900;
remainder mod 4 gives the phase: 0 new moon, 1 first quarter, 2 full moon,
3 last quarter."
  (let* ((phase (mod index 4))
         (index (/ index 4.0))
         (time (/ index 1236.85))
         (date (+ (calendar-absolute-from-gregorian '(1 0.5 1900))
                  0.75933
                  (* 29.53058868 index)
                  (* 0.0001178 time time)
                  (* -0.000000155 time time time)
                  (* 0.00033
                     (solar-sin-degrees (+ 166.56
                                           (* 132.87 time)
                                           (* -0.009173 time time))))))
         (sun-anomaly (mod
                       (+ 359.2242
                          (* 29.105356 index)
                          (* -0.0000333 time time)
                          (* -0.00000347 time time time))
                       360.0))
         (moon-anomaly (mod
                        (+ 306.0253
                           (* 385.81691806 index)
                           (* 0.0107306 time time)
                           (* 0.00001236 time time time))
                        360.0))
         (moon-lat (mod
                    (+ 21.2964
                       (* 390.67050646 index)
                       (* -0.0016528 time time)
                       (* -0.00000239 time time time))
                    360.0))
         (adjustment
          (if (memq phase '(0 2))
              (+ (* (- 0.1734 (* 0.000393 time))
                    (solar-sin-degrees sun-anomaly))
                 (* 0.0021 (solar-sin-degrees (* 2 sun-anomaly)))
                 (* -0.4068 (solar-sin-degrees moon-anomaly))
                 (* 0.0161 (solar-sin-degrees (* 2 moon-anomaly)))
                 (* -0.0004 (solar-sin-degrees (* 3 moon-anomaly)))
                 (* 0.0104 (solar-sin-degrees (* 2 moon-lat)))
                 (* -0.0051 (solar-sin-degrees (+ sun-anomaly moon-anomaly)))
                 (* -0.0074 (solar-sin-degrees (- sun-anomaly moon-anomaly)))
                 (* 0.0004 (solar-sin-degrees (+ (* 2 moon-lat) sun-anomaly)))
                 (* -0.0004 (solar-sin-degrees (- (* 2 moon-lat) sun-anomaly)))
                 (* -0.0006 (solar-sin-degrees
                             (+ (* 2 moon-lat) moon-anomaly)))
                 (* 0.0010 (solar-sin-degrees (- (* 2 moon-lat) moon-anomaly)))
                 (* 0.0005 (solar-sin-degrees
                            (+ (* 2 moon-anomaly) sun-anomaly))))
            (+ (* (- 0.1721 (* 0.0004 time))
                  (solar-sin-degrees sun-anomaly))
               (* 0.0021 (solar-sin-degrees (* 2 sun-anomaly)))
               (* -0.6280 (solar-sin-degrees moon-anomaly))
               (* 0.0089 (solar-sin-degrees (* 2 moon-anomaly)))
               (* -0.0004 (solar-sin-degrees (* 3 moon-anomaly)))
               (* 0.0079 (solar-sin-degrees (* 2 moon-lat)))
               (* -0.0119 (solar-sin-degrees (+ sun-anomaly moon-anomaly)))
               (* -0.0047 (solar-sin-degrees (- sun-anomaly moon-anomaly)))
               (* 0.0003 (solar-sin-degrees (+ (* 2 moon-lat) sun-anomaly)))
               (* -0.0004 (solar-sin-degrees (- (* 2 moon-lat) sun-anomaly)))
               (* -0.0006 (solar-sin-degrees (+ (* 2 moon-lat) moon-anomaly)))
               (* 0.0021 (solar-sin-degrees (- (* 2 moon-lat) moon-anomaly)))
               (* 0.0003 (solar-sin-degrees
                          (+ (* 2 moon-anomaly) sun-anomaly)))
               (* 0.0004 (solar-sin-degrees
                          (- sun-anomaly (* 2 moon-anomaly))))
               (* -0.0003 (solar-sin-degrees
                          (+ (* 2 sun-anomaly) moon-anomaly))))))
         (adj (+ 0.0028
                 (* -0.0004 (solar-cosine-degrees
                             sun-anomaly))
                 (* 0.0003 (solar-cosine-degrees
                            moon-anomaly))))
         (adjustment (cond ((= phase 1) (+ adjustment adj))
                           ((= phase 2) (- adjustment adj))
                           (t adjustment)))
         (date (+ date adjustment))
	 (date (+ date (/ (- calendar-time-zone
			     (solar-ephemeris-correction
                              (extract-calendar-year
                               (calendar-gregorian-from-absolute
                                (truncate date)))))
			  60.0 24.0)))
         (time (* 24 (- date (truncate date))))
	 (date (calendar-gregorian-from-absolute (truncate date)))
         (adj (dst-adjust-time date time)))
    (list (car adj) (apply 'solar-time-string (cdr adj)) phase)))

(defun lunar-phase-name (phase)
  "Name of lunar PHASE.
0 = new moon, 1 = first quarter, 2 = full moon, 3 = last quarter."
  (cond ((= 0 phase) "New Moon")
        ((= 1 phase) "First Quarter Moon")
        ((= 2 phase) "Full Moon")
        ((= 3 phase) "Last Quarter Moon")))

(defun calendar-phases-of-moon ()
  "Create a buffer with the lunar phases for the current calendar window."
  (interactive)
  (message "Computing phases of the moon...")
  (let ((m1 displayed-month)
        (y1 displayed-year)
        (m2 displayed-month)
        (y2 displayed-year))
    (increment-calendar-month m1 y1 -1)
    (increment-calendar-month m2 y2 1)
    (set-buffer (get-buffer-create lunar-phases-buffer))
    (setq buffer-read-only nil)
    (calendar-set-mode-line
     (if (= y1 y2)
         (format "Phases of the Moon from %s to %s, %d%%-"
                 (calendar-month-name m1) (calendar-month-name m2) y2)
       (format "Phases of the Moon from %s, %d to %s, %d%%-"
               (calendar-month-name m1) y1 (calendar-month-name m2) y2)))
    (erase-buffer)
    (insert
     (mapconcat
      '(lambda (x)
         (let ((date (car x))
               (time (car (cdr x)))
               (phase (car (cdr (cdr x)))))
           (concat (calendar-date-string date)
                   ": "
                   (lunar-phase-name phase)
                   " "
                   time)))
      (lunar-phase-list m1 y1) "\n"))
    (goto-char (point-min))
    (set-buffer-modified-p nil)
    (setq buffer-read-only t)
    (display-buffer lunar-phases-buffer)
    (message "Computing phases of the moon...done")))

;;;###autoload
(defun phases-of-moon (&optional arg)
  "Display the quarters of the moon for last month, this month, and next month.
If called with an optional prefix argument, prompts for month and year.

This function is suitable for execution in a .emacs file."
  (interactive "P")
  (save-excursion
    (let* ((date (if arg
                     (calendar-read-date t)
                   (calendar-current-date)))
           (displayed-month (extract-calendar-month date))
           (displayed-year (extract-calendar-year date)))
      (calendar-phases-of-moon))))

(defun diary-phases-of-moon ()
  "Moon phases diary entry."
  (let* ((index (* 4
                   (truncate
                    (* 12.3685
                       (+ (extract-calendar-year date)
                          ( / (calendar-day-number date)
                              366.0)
                          -1900)))))
         (phase (lunar-phase index)))
    (while (calendar-date-compare phase (list date))
      (setq index (1+ index))
      (setq phase (lunar-phase index)))
    (if (calendar-date-equal (car phase) date)
        (concat (lunar-phase-name (car (cdr (cdr phase)))) " "
                (car (cdr phase))))))


;;  For the Chinese calendar the calculations for the new moon need to be more
;;  accurate than those above, so we use more terms in the approximation.

(defun lunar-new-moon-time (k)
  "Astronomical (Julian) day number of K th new moon."
  (let* ((T (/ k 1236.85))
	 (T2 (* T T))
	 (T3 (* T T T))
	 (T4 (* T2 T2))
	 (JDE (+ 2451550.09765
		 (* 29.530588853 k)
		 (* 0.0001337 T2)
		 (* -0.000000150 T3)
		 (* 0.00000000073 T4)))
	 (E (- 1 (* 0.002516 T) (* 0.0000074 T2)))
	 (sun-anomaly (+ 2.5534
			 (* 29.10535669 k)
			 (* -0.0000218 T2)
			 (* -0.00000011 T3)))
	 (moon-anomaly (+ 201.5643
			  (* 385.81693528 k)
			  (* 0.0107438 T2)
			  (* 0.00001239 T3)
			  (* -0.000000058 T4)))
	 (moon-argument (+ 160.7108
			   (* 390.67050274 k)
			   (* -0.0016341 T2)
			   (* -0.00000227 T3)
			   (* 0.000000011 T4)))
	 (omega (+ 124.7746
		   (* -1.56375580 k)
		   (* 0.0020691 T2)
		   (* 0.00000215 T3)))
	 (A1  (+ 299.77 (*  0.107408 k) (* -0.009173 T2)))
	 (A2  (+ 251.88 (*  0.016321 k)))
	 (A3  (+ 251.83 (* 26.641886 k)))
	 (A4  (+ 349.42 (* 36.412478 k)))
	 (A5  (+  84.66 (* 18.206239 k)))
	 (A6  (+ 141.74 (* 53.303771 k)))
	 (A7  (+ 207.14 (*  2.453732 k)))
	 (A8  (+ 154.84 (*  7.306860 k)))
	 (A9  (+  34.52 (* 27.261239 k)))
	 (A10 (+ 207.19 (*  0.121824 k)))
	 (A11 (+ 291.34 (*  1.844379 k)))
	 (A12 (+ 161.72 (* 24.198154 k)))
	 (A13 (+ 239.56 (* 25.513099 k)))
	 (A14 (+ 331.55 (*  3.592518 k)))
	 (correction
	    (+ (* -0.40720   (solar-sin-degrees moon-anomaly))
	       (*  0.17241 E (solar-sin-degrees sun-anomaly))
	       (*  0.01608   (solar-sin-degrees (* 2 moon-anomaly)))
	       (*  0.01039   (solar-sin-degrees (* 2 moon-argument)))
	       (*  0.00739 E (solar-sin-degrees (- moon-anomaly sun-anomaly)))
	       (* -0.00514 E (solar-sin-degrees (+ moon-anomaly sun-anomaly)))
	       (*  0.00208 E E (solar-sin-degrees (* 2 sun-anomaly)))
	       (* -0.00111   (solar-sin-degrees
			       (- moon-anomaly (* 2 moon-argument))))
	       (* -0.00057   (solar-sin-degrees
			       (+ moon-anomaly (* 2 moon-argument))))
	       (*  0.00056 E (solar-sin-degrees
			       (+ (* 2 moon-anomaly) sun-anomaly)))
	       (* -0.00042   (solar-sin-degrees (* 3 moon-anomaly)))
	       (*  0.00042 E (solar-sin-degrees
			       (+ sun-anomaly (* 2 moon-argument))))
	       (*  0.00038 E (solar-sin-degrees
			       (- sun-anomaly (* 2 moon-argument))))
	       (* -0.00024 E (solar-sin-degrees
			       (- (* 2 moon-anomaly) sun-anomaly)))
	       (* -0.00017   (solar-sin-degrees omega))
	       (* -0.00007   (solar-sin-degrees
			       (+ moon-anomaly (* 2 sun-anomaly))))
	       (*  0.00004   (solar-sin-degrees
			       (- (* 2 moon-anomaly) (* 2 moon-argument))))
	       (*  0.00004   (solar-sin-degrees (* 3 sun-anomaly)))
	       (*  0.00003   (solar-sin-degrees (+ moon-anomaly sun-anomaly
						   (* -2 moon-argument))))
	       (*  0.00003   (solar-sin-degrees
			       (+ (* 2 moon-anomaly) (* 2 moon-argument))))
	       (* -0.00003   (solar-sin-degrees (+ moon-anomaly sun-anomaly
						   (* 2 moon-argument))))
	       (*  0.00003   (solar-sin-degrees (- moon-anomaly sun-anomaly
						   (* -2 moon-argument))))
	       (* -0.00002   (solar-sin-degrees (- moon-anomaly sun-anomaly
						   (* 2 moon-argument))))
	       (* -0.00002   (solar-sin-degrees
			       (+ (* 3 moon-anomaly) sun-anomaly)))
	       (*  0.00002   (solar-sin-degrees (* 4 moon-anomaly)))))
	 (additional
	    (+ (* 0.000325 (solar-sin-degrees A1))
	       (* 0.000165 (solar-sin-degrees A2))
	       (* 0.000164 (solar-sin-degrees A3))
	       (* 0.000126 (solar-sin-degrees A4))
	       (* 0.000110 (solar-sin-degrees A5))
	       (* 0.000062 (solar-sin-degrees A6))
	       (* 0.000060 (solar-sin-degrees A7))
	       (* 0.000056 (solar-sin-degrees A8))
	       (* 0.000047 (solar-sin-degrees A9))
	       (* 0.000042 (solar-sin-degrees A10))
	       (* 0.000040 (solar-sin-degrees A11))
	       (* 0.000037 (solar-sin-degrees A12))
	       (* 0.000035 (solar-sin-degrees A13))
	       (* 0.000023 (solar-sin-degrees A14))))
	 (newJDE (+ JDE correction additional)))
    (+ newJDE
       (- (solar-ephemeris-correction
           (extract-calendar-year
            (calendar-gregorian-from-absolute
             (floor (calendar-absolute-from-astro newJDE))))))
       (/ calendar-time-zone 60.0 24.0))))

(defun lunar-new-moon-on-or-after (d)
  "Astronomical (Julian) day number of first new moon on or after astronomical
\(Julian) day number d.  The fractional part is the time of day.

The date and time are local time, including any daylight savings rules,
as governed by the values of calendar-daylight-savings-starts,
calendar-daylight-savings-starts-time, calendar-daylight-savings-ends,
calendar-daylight-savings-ends-time, calendar-daylight-time-offset, and
calendar-time-zone."
  (let* ((date (calendar-gregorian-from-absolute
                (floor (calendar-absolute-from-astro d))))
         (year (+ (extract-calendar-year date)
		  (/ (calendar-day-number date) 365.25)))
	 (k (floor (* (- year 2000.0) 12.3685)))
         (date (lunar-new-moon-time k)))
    (while (< date d)
      (setq k (1+ k))
      (setq date (lunar-new-moon-time k)))
    (let* ((a-date (calendar-absolute-from-astro date))
           (time (* 24 (- a-date (truncate a-date))))
           (date (calendar-gregorian-from-absolute (truncate a-date)))
           (adj (dst-adjust-time date time)))
      (calendar-astro-from-absolute
       (+ (calendar-absolute-from-gregorian (car adj))
          (/ (car (cdr adj)) 24.0))))))

(provide 'lunar)

;;; lunar.el ends here
Commit	Line	Data
7e1dae73 JB	1	;;; lunar.el --- calendar functions for phases of the moon.
7e1dae73 JB	2
a96a5fca	3	;; Copyright (C) 1992, 1993, 1995, 1997 Free Software Foundation, Inc.
7e1dae73 JB	4
7e1dae73 JB	5	;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
e9571d2a ER	6	;; Keywords: calendar
e9571d2a ER	7	;; Human-Keywords: moon, lunar phases, calendar, diary
7e1dae73 JB	8
	9	;; This file is part of GNU Emacs.
	10
59243403 RS	11	;; GNU Emacs is free software; you can redistribute it and/or modify
	12	;; it under the terms of the GNU General Public License as published by
	13	;; the Free Software Foundation; either version 2, or (at your option)
	14	;; any later version.
	15
7e1dae73	16	;; GNU Emacs is distributed in the hope that it will be useful,
59243403 RS	17	;; but WITHOUT ANY WARRANTY; without even the implied warranty of
	18	;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	19	;; GNU General Public License for more details.
	20
	21	;; You should have received a copy of the GNU General Public License
b578f267 EN	22	;; along with GNU Emacs; see the file COPYING. If not, write to the
	23	;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
	24	;; Boston, MA 02111-1307, USA.
7e1dae73 JB	25
	26	;;; Commentary:
	27
	28	;; This collection of functions implements lunar phases for calendar.el and
	29	;; diary.el.
	30
	31	;; Based on ``Astronomical Formulae for Calculators,'' 3rd ed., by Jean Meeus,
8a45b040 ER	32	;; Willmann-Bell, Inc., 1985 and ``Astronomical Algorithms'' by Jean Meeus,
8a45b040 ER	33	;; Willmann-Bell, Inc., 1991.
7e1dae73 JB	34	;;
	35	;; WARNING: The calculations will be accurate only to within a few minutes.
	36
	37	;; The author would be delighted to have an astronomically more sophisticated
	38	;; person rewrite the code for the lunar calculations in this file!
	39
a96a5fca PE	40	;; Technical details of all the calendrical calculations can be found in
	41	;; ``Calendrical Calculations'' by Nachum Dershowitz and Edward M. Reingold,
	42	;; Cambridge University Press (1997).
	43
7e1dae73 JB	44	;; Comments, corrections, and improvements should be sent to
	45	;; Edward M. Reingold Department of Computer Science
	46	;; (217) 333-6733 University of Illinois at Urbana-Champaign
	47	;; reingold@cs.uiuc.edu 1304 West Springfield Avenue
	48	;; Urbana, Illinois 61801
	49
	50	;;; Code:
	51
	52	(if (fboundp 'atan)
	53	(require 'lisp-float-type)
	54	(error "Lunar calculations impossible since floating point is unavailable."))
	55
	56	(require 'solar)
	57
	58	(defun lunar-phase-list (month year)
	59	"List of lunar phases for three months starting with Gregorian MONTH, YEAR."
	60	(let ((end-month month)
	61	(end-year year)
	62	(start-month month)
	63	(start-year year))
	64	(increment-calendar-month end-month end-year 3)
	65	(increment-calendar-month start-month start-year -1)
	66	(let* ((end-date (list (list end-month 1 end-year)))
	67	(start-date (list (list start-month
	68	(calendar-last-day-of-month
	69	start-month start-year)
	70	start-year)))
	71	(index (* 4
	72	(truncate
	73	(* 12.3685
	74	(+ year
	75	( / (calendar-day-number (list month 1 year))
	76	366.0)
	77	-1900)))))
	78	(new-moon (lunar-phase index))
	79	(list))
	80	(while (calendar-date-compare new-moon end-date)
	81	(if (calendar-date-compare start-date new-moon)
	82	(setq list (append list (list new-moon))))
	83	(setq index (1+ index))
	84	(setq new-moon (lunar-phase index)))
	85	list)))
	86
	87	(defun lunar-phase (index)
	88	"Local date and time of lunar phase INDEX.
	89	Integer below INDEX/4 gives the lunation number, counting from Jan 1, 1900;
	90	remainder mod 4 gives the phase: 0 new moon, 1 first quarter, 2 full moon,
	91	3 last quarter."
b6c0aabf	92	(let* ((phase (mod index 4))
7e1dae73 JB	93	(index (/ index 4.0))
	94	(time (/ index 1236.85))
	95	(date (+ (calendar-absolute-from-gregorian '(1 0.5 1900))
	96	0.75933
	97	(* 29.53058868 index)
	98	(* 0.0001178 time time)
	99	(* -0.000000155 time time time)
	100	(* 0.00033
	101	(solar-sin-degrees (+ 166.56
	102	(* 132.87 time)
	103	(* -0.009173 time time))))))
e7bb3aeb	104	(sun-anomaly (mod
7e1dae73 JB	105	(+ 359.2242
	106	(* 29.105356 index)
	107	(* -0.0000333 time time)
	108	(* -0.00000347 time time time))
	109	360.0))
e7bb3aeb	110	(moon-anomaly (mod
7e1dae73 JB	111	(+ 306.0253
	112	(* 385.81691806 index)
	113	(* 0.0107306 time time)
	114	(* 0.00001236 time time time))
	115	360.0))
e7bb3aeb	116	(moon-lat (mod
7e1dae73 JB	117	(+ 21.2964
	118	(* 390.67050646 index)
	119	(* -0.0016528 time time)
	120	(* -0.00000239 time time time))
	121	360.0))
	122	(adjustment
	123	(if (memq phase '(0 2))
	124	(+ (* (- 0.1734 (* 0.000393 time))
	125	(solar-sin-degrees sun-anomaly))
	126	(* 0.0021 (solar-sin-degrees (* 2 sun-anomaly)))
	127	(* -0.4068 (solar-sin-degrees moon-anomaly))
	128	(* 0.0161 (solar-sin-degrees (* 2 moon-anomaly)))
	129	(* -0.0004 (solar-sin-degrees (* 3 moon-anomaly)))
	130	(* 0.0104 (solar-sin-degrees (* 2 moon-lat)))
	131	(* -0.0051 (solar-sin-degrees (+ sun-anomaly moon-anomaly)))
	132	(* -0.0074 (solar-sin-degrees (- sun-anomaly moon-anomaly)))
	133	(* 0.0004 (solar-sin-degrees (+ (* 2 moon-lat) sun-anomaly)))
	134	(* -0.0004 (solar-sin-degrees (- (* 2 moon-lat) sun-anomaly)))
	135	(* -0.0006 (solar-sin-degrees
	136	(+ (* 2 moon-lat) moon-anomaly)))
	137	(* 0.0010 (solar-sin-degrees (- (* 2 moon-lat) moon-anomaly)))
	138	(* 0.0005 (solar-sin-degrees
	139	(+ (* 2 moon-anomaly) sun-anomaly))))
	140	(+ (* (- 0.1721 (* 0.0004 time))
	141	(solar-sin-degrees sun-anomaly))
	142	(* 0.0021 (solar-sin-degrees (* 2 sun-anomaly)))
	143	(* -0.6280 (solar-sin-degrees moon-anomaly))
	144	(* 0.0089 (solar-sin-degrees (* 2 moon-anomaly)))
	145	(* -0.0004 (solar-sin-degrees (* 3 moon-anomaly)))
	146	(* 0.0079 (solar-sin-degrees (* 2 moon-lat)))
	147	(* -0.0119 (solar-sin-degrees (+ sun-anomaly moon-anomaly)))
	148	(* -0.0047 (solar-sin-degrees (- sun-anomaly moon-anomaly)))
	149	(* 0.0003 (solar-sin-degrees (+ (* 2 moon-lat) sun-anomaly)))
	150	(* -0.0004 (solar-sin-degrees (- (* 2 moon-lat) sun-anomaly)))
	151	(* -0.0006 (solar-sin-degrees (+ (* 2 moon-lat) moon-anomaly)))
	152	(* 0.0021 (solar-sin-degrees (- (* 2 moon-lat) moon-anomaly)))
	153	(* 0.0003 (solar-sin-degrees
	154	(+ (* 2 moon-anomaly) sun-anomaly)))
	155	(* 0.0004 (solar-sin-degrees
	156	(- sun-anomaly (* 2 moon-anomaly))))
	157	(* -0.0003 (solar-sin-degrees
	158	(+ (* 2 sun-anomaly) moon-anomaly))))))
	159	(adj (+ 0.0028
	160	(* -0.0004 (solar-cosine-degrees
	161	sun-anomaly))
	162	(* 0.0003 (solar-cosine-degrees
	163	moon-anomaly))))
	164	(adjustment (cond ((= phase 1) (+ adjustment adj))
	165	((= phase 2) (- adjustment adj))
	166	(t adjustment)))
	167	(date (+ date adjustment))
238c5cc1 PE	168	(date (+ date (/ (- calendar-time-zone
238c5cc1 PE	169	(solar-ephemeris-correction
80e48f9f JB	170	(extract-calendar-year
80e48f9f JB	171	(calendar-gregorian-from-absolute
238c5cc1 PE	172	(truncate date)))))
238c5cc1 PE	173	60.0 24.0)))
7e1dae73	174	(time (* 24 (- date (truncate date))))
e483c805	175	(date (calendar-gregorian-from-absolute (truncate date)))
8a45b040	176	(adj (dst-adjust-time date time)))
e483c805	177	(list (car adj) (apply 'solar-time-string (cdr adj)) phase)))
7e1dae73 JB	178
	179	(defun lunar-phase-name (phase)
	180	"Name of lunar PHASE.
	181	0 = new moon, 1 = first quarter, 2 = full moon, 3 = last quarter."
	182	(cond ((= 0 phase) "New Moon")
	183	((= 1 phase) "First Quarter Moon")
	184	((= 2 phase) "Full Moon")
	185	((= 3 phase) "Last Quarter Moon")))
	186
	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)
cc4879d2	194	(y2 displayed-year))
7e1dae73 JB	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
1a380827 RS	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)))
7e1dae73 JB	205	(erase-buffer)
	206	(insert
	207	(mapconcat
	208	'(lambda (x)
	209	(let ((date (car x))
	210	(time (car (cdr x)))
	211	(phase (car (cdr (cdr x)))))
	212	(concat (calendar-date-string date)
	213	": "
	214	(lunar-phase-name phase)
	215	" "
	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")))
	223
	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, prompts for month and year.
	228
	229	This function is suitable for execution in a .emacs file."
	230	(interactive "P")
	231	(save-excursion
46124264	232	(let* ((date (if arg
cc4879d2 ER	233	(calendar-read-date t)
	234	(calendar-current-date)))
	235	(displayed-month (extract-calendar-month date))
	236	(displayed-year (extract-calendar-year date)))
7e1dae73 JB	237	(calendar-phases-of-moon))))
	238
	239	(defun diary-phases-of-moon ()
	240	"Moon phases diary entry."
	241	(let* ((index (* 4
	242	(truncate
	243	(* 12.3685
	244	(+ (extract-calendar-year date)
	245	( / (calendar-day-number date)
	246	366.0)
	247	-1900)))))
	248	(phase (lunar-phase index)))
	249	(while (calendar-date-compare phase (list date))
	250	(setq index (1+ index))
	251	(setq phase (lunar-phase index)))
	252	(if (calendar-date-equal (car phase) date)
	253	(concat (lunar-phase-name (car (cdr (cdr phase)))) " "
	254	(car (cdr phase))))))
	255
8a45b040 ER	256
	257	;; For the Chinese calendar the calculations for the new moon need to be more
	258	;; accurate than those above, so we use more terms in the approximation.
	259
	260	(defun lunar-new-moon-time (k)
	261	"Astronomical (Julian) day number of K th new moon."
	262	(let* ((T (/ k 1236.85))
	263	(T2 (* T T))
	264	(T3 (* T T T))
	265	(T4 (* T2 T2))
	266	(JDE (+ 2451550.09765
	267	(* 29.530588853 k)
	268	(* 0.0001337 T2)
	269	(* -0.000000150 T3)
	270	(* 0.00000000073 T4)))
	271	(E (- 1 (* 0.002516 T) (* 0.0000074 T2)))
	272	(sun-anomaly (+ 2.5534
	273	(* 29.10535669 k)
	274	(* -0.0000218 T2)
	275	(* -0.00000011 T3)))
	276	(moon-anomaly (+ 201.5643
	277	(* 385.81693528 k)
	278	(* 0.0107438 T2)
	279	(* 0.00001239 T3)
	280	(* -0.000000058 T4)))
	281	(moon-argument (+ 160.7108
	282	(* 390.67050274 k)
	283	(* -0.0016341 T2)
	284	(* -0.00000227 T3)
	285	(* 0.000000011 T4)))
	286	(omega (+ 124.7746
	287	(* -1.56375580 k)
	288	(* 0.0020691 T2)
	289	(* 0.00000215 T3)))
	290	(A1 (+ 299.77 (* 0.107408 k) (* -0.009173 T2)))
	291	(A2 (+ 251.88 (* 0.016321 k)))
	292	(A3 (+ 251.83 (* 26.641886 k)))
	293	(A4 (+ 349.42 (* 36.412478 k)))
	294	(A5 (+ 84.66 (* 18.206239 k)))
	295	(A6 (+ 141.74 (* 53.303771 k)))
	296	(A7 (+ 207.14 (* 2.453732 k)))
	297	(A8 (+ 154.84 (* 7.306860 k)))
	298	(A9 (+ 34.52 (* 27.261239 k)))
	299	(A10 (+ 207.19 (* 0.121824 k)))
	300	(A11 (+ 291.34 (* 1.844379 k)))
	301	(A12 (+ 161.72 (* 24.198154 k)))
	302	(A13 (+ 239.56 (* 25.513099 k)))
	303	(A14 (+ 331.55 (* 3.592518 k)))
	304	(correction
	305	(+ (* -0.40720 (solar-sin-degrees moon-anomaly))
	306	(* 0.17241 E (solar-sin-degrees sun-anomaly))
	307	(* 0.01608 (solar-sin-degrees (* 2 moon-anomaly)))
	308	(* 0.01039 (solar-sin-degrees (* 2 moon-argument)))
	309	(* 0.00739 E (solar-sin-degrees (- moon-anomaly sun-anomaly)))
	310	(* -0.00514 E (solar-sin-degrees (+ moon-anomaly sun-anomaly)))
	311	(* 0.00208 E E (solar-sin-degrees (* 2 sun-anomaly)))
	312	(* -0.00111 (solar-sin-degrees
	313	(- moon-anomaly (* 2 moon-argument))))
	314	(* -0.00057 (solar-sin-degrees
	315	(+ moon-anomaly (* 2 moon-argument))))
	316	(* 0.00056 E (solar-sin-degrees
	317	(+ (* 2 moon-anomaly) sun-anomaly)))
	318	(* -0.00042 (solar-sin-degrees (* 3 moon-anomaly)))
	319	(* 0.00042 E (solar-sin-degrees
320	(+ sun-anomaly (* 2 moon-argument))))
321	(* 0.00038 E (solar-sin-degrees
322	(- sun-anomaly (* 2 moon-argument))))
323	(* -0.00024 E (solar-sin-degrees
324	(- (* 2 moon-anomaly) sun-anomaly)))
325	(* -0.00017 (solar-sin-degrees omega))
326	(* -0.00007 (solar-sin-degrees
327	(+ moon-anomaly (* 2 sun-anomaly))))
328	(* 0.00004 (solar-sin-degrees
329	(- (* 2 moon-anomaly) (* 2 moon-argument))))
330	(* 0.00004 (solar-sin-degrees (* 3 sun-anomaly)))
331	(* 0.00003 (solar-sin-degrees (+ moon-anomaly sun-anomaly
332	(* -2 moon-argument))))
333	(* 0.00003 (solar-sin-degrees
334	(+ (* 2 moon-anomaly) (* 2 moon-argument))))
335	(* -0.00003 (solar-sin-degrees (+ moon-anomaly sun-anomaly
336	(* 2 moon-argument))))
337	(* 0.00003 (solar-sin-degrees (- moon-anomaly sun-anomaly
338	(* -2 moon-argument))))
339	(* -0.00002 (solar-sin-degrees (- moon-anomaly sun-anomaly
340	(* 2 moon-argument))))
341	(* -0.00002 (solar-sin-degrees
342	(+ (* 3 moon-anomaly) sun-anomaly)))
343	(* 0.00002 (solar-sin-degrees (* 4 moon-anomaly)))))
344	(additional
345	(+ (* 0.000325 (solar-sin-degrees A1))
346	(* 0.000165 (solar-sin-degrees A2))
347	(* 0.000164 (solar-sin-degrees A3))
348	(* 0.000126 (solar-sin-degrees A4))
349	(* 0.000110 (solar-sin-degrees A5))
350	(* 0.000062 (solar-sin-degrees A6))
351	(* 0.000060 (solar-sin-degrees A7))
352	(* 0.000056 (solar-sin-degrees A8))
353	(* 0.000047 (solar-sin-degrees A9))
354	(* 0.000042 (solar-sin-degrees A10))
355	(* 0.000040 (solar-sin-degrees A11))
356	(* 0.000037 (solar-sin-degrees A12))
357	(* 0.000035 (solar-sin-degrees A13))
358	(* 0.000023 (solar-sin-degrees A14))))
359	(newJDE (+ JDE correction additional)))
360	(+ newJDE
361	(- (solar-ephemeris-correction
362	(extract-calendar-year
363	(calendar-gregorian-from-absolute
364	(floor (calendar-absolute-from-astro newJDE))))))
365	(/ calendar-time-zone 60.0 24.0))))
366
367	(defun lunar-new-moon-on-or-after (d)
368	"Astronomical (Julian) day number of first new moon on or after astronomical
3001419f	369	\(Julian) day number d. The fractional part is the time of day.
8a45b040 ER	370
	371	The date and time are local time, including any daylight savings rules,
	372	as governed by the values of calendar-daylight-savings-starts,
	373	calendar-daylight-savings-starts-time, calendar-daylight-savings-ends,
	374	calendar-daylight-savings-ends-time, calendar-daylight-time-offset, and
	375	calendar-time-zone."
	376	(let* ((date (calendar-gregorian-from-absolute
	377	(floor (calendar-absolute-from-astro d))))
	378	(year (+ (extract-calendar-year date)
	379	(/ (calendar-day-number date) 365.25)))
	380	(k (floor (* (- year 2000.0) 12.3685)))
	381	(date (lunar-new-moon-time k)))
	382	(while (< date d)
	383	(setq k (1+ k))
	384	(setq date (lunar-new-moon-time k)))
	385	(let* ((a-date (calendar-absolute-from-astro date))
	386	(time (* 24 (- a-date (truncate a-date))))
	387	(date (calendar-gregorian-from-absolute (truncate a-date)))
	388	(adj (dst-adjust-time date time)))
	389	(calendar-astro-from-absolute
	390	(+ (calendar-absolute-from-gregorian (car adj))
	391	(/ (car (cdr adj)) 24.0))))))
	392
7e1dae73 JB	393	(provide 'lunar)
	394
	395	;;; lunar.el ends here