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

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

;; Copyright (C) 1992, 1993, 1995 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!

;; 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
8a45b040	3	;; Copyright (C) 1992, 1993, 1995 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
	40	;; Comments, corrections, and improvements should be sent to
	41	;; Edward M. Reingold Department of Computer Science
	42	;; (217) 333-6733 University of Illinois at Urbana-Champaign
	43	;; reingold@cs.uiuc.edu 1304 West Springfield Avenue
	44	;; Urbana, Illinois 61801
	45
	46	;;; Code:
	47
	48	(if (fboundp 'atan)
	49	(require 'lisp-float-type)
	50	(error "Lunar calculations impossible since floating point is unavailable."))
	51
	52	(require 'solar)
	53
	54	(defun lunar-phase-list (month year)
	55	"List of lunar phases for three months starting with Gregorian MONTH, YEAR."
	56	(let ((end-month month)
	57	(end-year year)
	58	(start-month month)
	59	(start-year year))
	60	(increment-calendar-month end-month end-year 3)
	61	(increment-calendar-month start-month start-year -1)
	62	(let* ((end-date (list (list end-month 1 end-year)))
	63	(start-date (list (list start-month
	64	(calendar-last-day-of-month
	65	start-month start-year)
	66	start-year)))
	67	(index (* 4
	68	(truncate
	69	(* 12.3685
	70	(+ year
	71	( / (calendar-day-number (list month 1 year))
	72	366.0)
	73	-1900)))))
	74	(new-moon (lunar-phase index))
	75	(list))
	76	(while (calendar-date-compare new-moon end-date)
	77	(if (calendar-date-compare start-date new-moon)
	78	(setq list (append list (list new-moon))))
	79	(setq index (1+ index))
	80	(setq new-moon (lunar-phase index)))
	81	list)))
	82
	83	(defun lunar-phase (index)
	84	"Local date and time of lunar phase INDEX.
	85	Integer below INDEX/4 gives the lunation number, counting from Jan 1, 1900;
	86	remainder mod 4 gives the phase: 0 new moon, 1 first quarter, 2 full moon,
	87	3 last quarter."
b6c0aabf	88	(let* ((phase (mod index 4))
7e1dae73 JB	89	(index (/ index 4.0))
	90	(time (/ index 1236.85))
	91	(date (+ (calendar-absolute-from-gregorian '(1 0.5 1900))
	92	0.75933
	93	(* 29.53058868 index)
	94	(* 0.0001178 time time)
	95	(* -0.000000155 time time time)
	96	(* 0.00033
	97	(solar-sin-degrees (+ 166.56
	98	(* 132.87 time)
	99	(* -0.009173 time time))))))
e7bb3aeb	100	(sun-anomaly (mod
7e1dae73 JB	101	(+ 359.2242
	102	(* 29.105356 index)
	103	(* -0.0000333 time time)
	104	(* -0.00000347 time time time))
	105	360.0))
e7bb3aeb	106	(moon-anomaly (mod
7e1dae73 JB	107	(+ 306.0253
	108	(* 385.81691806 index)
	109	(* 0.0107306 time time)
	110	(* 0.00001236 time time time))
	111	360.0))
e7bb3aeb	112	(moon-lat (mod
7e1dae73 JB	113	(+ 21.2964
	114	(* 390.67050646 index)
	115	(* -0.0016528 time time)
	116	(* -0.00000239 time time time))
	117	360.0))
	118	(adjustment
	119	(if (memq phase '(0 2))
	120	(+ (* (- 0.1734 (* 0.000393 time))
	121	(solar-sin-degrees sun-anomaly))
	122	(* 0.0021 (solar-sin-degrees (* 2 sun-anomaly)))
	123	(* -0.4068 (solar-sin-degrees moon-anomaly))
	124	(* 0.0161 (solar-sin-degrees (* 2 moon-anomaly)))
	125	(* -0.0004 (solar-sin-degrees (* 3 moon-anomaly)))
	126	(* 0.0104 (solar-sin-degrees (* 2 moon-lat)))
	127	(* -0.0051 (solar-sin-degrees (+ sun-anomaly moon-anomaly)))
	128	(* -0.0074 (solar-sin-degrees (- sun-anomaly moon-anomaly)))
	129	(* 0.0004 (solar-sin-degrees (+ (* 2 moon-lat) sun-anomaly)))
	130	(* -0.0004 (solar-sin-degrees (- (* 2 moon-lat) sun-anomaly)))
	131	(* -0.0006 (solar-sin-degrees
	132	(+ (* 2 moon-lat) moon-anomaly)))
	133	(* 0.0010 (solar-sin-degrees (- (* 2 moon-lat) moon-anomaly)))
	134	(* 0.0005 (solar-sin-degrees
	135	(+ (* 2 moon-anomaly) sun-anomaly))))
	136	(+ (* (- 0.1721 (* 0.0004 time))
	137	(solar-sin-degrees sun-anomaly))
	138	(* 0.0021 (solar-sin-degrees (* 2 sun-anomaly)))
	139	(* -0.6280 (solar-sin-degrees moon-anomaly))
	140	(* 0.0089 (solar-sin-degrees (* 2 moon-anomaly)))
	141	(* -0.0004 (solar-sin-degrees (* 3 moon-anomaly)))
	142	(* 0.0079 (solar-sin-degrees (* 2 moon-lat)))
	143	(* -0.0119 (solar-sin-degrees (+ sun-anomaly moon-anomaly)))
	144	(* -0.0047 (solar-sin-degrees (- sun-anomaly moon-anomaly)))
	145	(* 0.0003 (solar-sin-degrees (+ (* 2 moon-lat) sun-anomaly)))
	146	(* -0.0004 (solar-sin-degrees (- (* 2 moon-lat) sun-anomaly)))
	147	(* -0.0006 (solar-sin-degrees (+ (* 2 moon-lat) moon-anomaly)))
	148	(* 0.0021 (solar-sin-degrees (- (* 2 moon-lat) moon-anomaly)))
	149	(* 0.0003 (solar-sin-degrees
	150	(+ (* 2 moon-anomaly) sun-anomaly)))
	151	(* 0.0004 (solar-sin-degrees
	152	(- sun-anomaly (* 2 moon-anomaly))))
	153	(* -0.0003 (solar-sin-degrees
	154	(+ (* 2 sun-anomaly) moon-anomaly))))))
	155	(adj (+ 0.0028
	156	(* -0.0004 (solar-cosine-degrees
	157	sun-anomaly))
	158	(* 0.0003 (solar-cosine-degrees
	159	moon-anomaly))))
	160	(adjustment (cond ((= phase 1) (+ adjustment adj))
	161	((= phase 2) (- adjustment adj))
	162	(t adjustment)))
	163	(date (+ date adjustment))
238c5cc1 PE	164	(date (+ date (/ (- calendar-time-zone
238c5cc1 PE	165	(solar-ephemeris-correction
80e48f9f JB	166	(extract-calendar-year
80e48f9f JB	167	(calendar-gregorian-from-absolute
238c5cc1 PE	168	(truncate date)))))
238c5cc1 PE	169	60.0 24.0)))
7e1dae73	170	(time (* 24 (- date (truncate date))))
e483c805	171	(date (calendar-gregorian-from-absolute (truncate date)))
8a45b040	172	(adj (dst-adjust-time date time)))
e483c805	173	(list (car adj) (apply 'solar-time-string (cdr adj)) phase)))
7e1dae73 JB	174
	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")))
	182
	183	(defun calendar-phases-of-moon ()
	184	"Create a buffer with the lunar phases for the current calendar window."
	185	(interactive)
	186	(message "Computing phases of the moon...")
	187	(let ((m1 displayed-month)
	188	(y1 displayed-year)
	189	(m2 displayed-month)
cc4879d2	190	(y2 displayed-year))
7e1dae73 JB	191	(increment-calendar-month m1 y1 -1)
	192	(increment-calendar-month m2 y2 1)
	193	(set-buffer (get-buffer-create lunar-phases-buffer))
	194	(setq buffer-read-only nil)
	195	(calendar-set-mode-line
1a380827 RS	196	(if (= y1 y2)
	197	(format "Phases of the Moon from %s to %s, %d%%-"
	198	(calendar-month-name m1) (calendar-month-name m2) y2)
	199	(format "Phases of the Moon from %s, %d to %s, %d%%-"
	200	(calendar-month-name m1) y1 (calendar-month-name m2) y2)))
7e1dae73 JB	201	(erase-buffer)
	202	(insert
	203	(mapconcat
	204	'(lambda (x)
	205	(let ((date (car x))
	206	(time (car (cdr x)))
	207	(phase (car (cdr (cdr x)))))
	208	(concat (calendar-date-string date)
	209	": "
	210	(lunar-phase-name phase)
	211	" "
	212	time)))
	213	(lunar-phase-list m1 y1) "\n"))
	214	(goto-char (point-min))
	215	(set-buffer-modified-p nil)
	216	(setq buffer-read-only t)
	217	(display-buffer lunar-phases-buffer)
	218	(message "Computing phases of the moon...done")))
	219
	220	;;;###autoload
	221	(defun phases-of-moon (&optional arg)
	222	"Display the quarters of the moon for last month, this month, and next month.
	223	If called with an optional prefix argument, prompts for month and year.
	224
	225	This function is suitable for execution in a .emacs file."
	226	(interactive "P")
	227	(save-excursion
46124264	228	(let* ((date (if arg
cc4879d2 ER	229	(calendar-read-date t)
	230	(calendar-current-date)))
	231	(displayed-month (extract-calendar-month date))
	232	(displayed-year (extract-calendar-year date)))
7e1dae73 JB	233	(calendar-phases-of-moon))))
	234
	235	(defun diary-phases-of-moon ()
	236	"Moon phases diary entry."
	237	(let* ((index (* 4
	238	(truncate
	239	(* 12.3685
	240	(+ (extract-calendar-year date)
	241	( / (calendar-day-number date)
	242	366.0)
	243	-1900)))))
	244	(phase (lunar-phase index)))
	245	(while (calendar-date-compare phase (list date))
	246	(setq index (1+ index))
	247	(setq phase (lunar-phase index)))
	248	(if (calendar-date-equal (car phase) date)
	249	(concat (lunar-phase-name (car (cdr (cdr phase)))) " "
	250	(car (cdr phase))))))
	251
8a45b040 ER	252
	253	;; For the Chinese calendar the calculations for the new moon need to be more
	254	;; accurate than those above, so we use more terms in the approximation.
	255
	256	(defun lunar-new-moon-time (k)
	257	"Astronomical (Julian) day number of K th new moon."
	258	(let* ((T (/ k 1236.85))
	259	(T2 (* T T))
	260	(T3 (* T T T))
	261	(T4 (* T2 T2))
	262	(JDE (+ 2451550.09765
	263	(* 29.530588853 k)
	264	(* 0.0001337 T2)
	265	(* -0.000000150 T3)
	266	(* 0.00000000073 T4)))
	267	(E (- 1 (* 0.002516 T) (* 0.0000074 T2)))
	268	(sun-anomaly (+ 2.5534
	269	(* 29.10535669 k)
	270	(* -0.0000218 T2)
	271	(* -0.00000011 T3)))
	272	(moon-anomaly (+ 201.5643
	273	(* 385.81693528 k)
	274	(* 0.0107438 T2)
	275	(* 0.00001239 T3)
	276	(* -0.000000058 T4)))
	277	(moon-argument (+ 160.7108
	278	(* 390.67050274 k)
	279	(* -0.0016341 T2)
	280	(* -0.00000227 T3)
	281	(* 0.000000011 T4)))
	282	(omega (+ 124.7746
	283	(* -1.56375580 k)
	284	(* 0.0020691 T2)
	285	(* 0.00000215 T3)))
	286	(A1 (+ 299.77 (* 0.107408 k) (* -0.009173 T2)))
	287	(A2 (+ 251.88 (* 0.016321 k)))
	288	(A3 (+ 251.83 (* 26.641886 k)))
	289	(A4 (+ 349.42 (* 36.412478 k)))
	290	(A5 (+ 84.66 (* 18.206239 k)))
	291	(A6 (+ 141.74 (* 53.303771 k)))
	292	(A7 (+ 207.14 (* 2.453732 k)))
	293	(A8 (+ 154.84 (* 7.306860 k)))
	294	(A9 (+ 34.52 (* 27.261239 k)))
	295	(A10 (+ 207.19 (* 0.121824 k)))
	296	(A11 (+ 291.34 (* 1.844379 k)))
	297	(A12 (+ 161.72 (* 24.198154 k)))
	298	(A13 (+ 239.56 (* 25.513099 k)))
	299	(A14 (+ 331.55 (* 3.592518 k)))
	300	(correction
	301	(+ (* -0.40720 (solar-sin-degrees moon-anomaly))
	302	(* 0.17241 E (solar-sin-degrees sun-anomaly))
	303	(* 0.01608 (solar-sin-degrees (* 2 moon-anomaly)))
	304	(* 0.01039 (solar-sin-degrees (* 2 moon-argument)))
	305	(* 0.00739 E (solar-sin-degrees (- moon-anomaly sun-anomaly)))
	306	(* -0.00514 E (solar-sin-degrees (+ moon-anomaly sun-anomaly)))
	307	(* 0.00208 E E (solar-sin-degrees (* 2 sun-anomaly)))
	308	(* -0.00111 (solar-sin-degrees
	309	(- moon-anomaly (* 2 moon-argument))))
	310	(* -0.00057 (solar-sin-degrees
	311	(+ moon-anomaly (* 2 moon-argument))))
	312	(* 0.00056 E (solar-sin-degrees
	313	(+ (* 2 moon-anomaly) sun-anomaly)))
	314	(* -0.00042 (solar-sin-degrees (* 3 moon-anomaly)))
	315	(* 0.00042 E (solar-sin-degrees
316	(+ sun-anomaly (* 2 moon-argument))))
317	(* 0.00038 E (solar-sin-degrees
318	(- sun-anomaly (* 2 moon-argument))))
319	(* -0.00024 E (solar-sin-degrees
320	(- (* 2 moon-anomaly) sun-anomaly)))
321	(* -0.00017 (solar-sin-degrees omega))
322	(* -0.00007 (solar-sin-degrees
323	(+ moon-anomaly (* 2 sun-anomaly))))
324	(* 0.00004 (solar-sin-degrees
325	(- (* 2 moon-anomaly) (* 2 moon-argument))))
326	(* 0.00004 (solar-sin-degrees (* 3 sun-anomaly)))
327	(* 0.00003 (solar-sin-degrees (+ moon-anomaly sun-anomaly
328	(* -2 moon-argument))))
329	(* 0.00003 (solar-sin-degrees
330	(+ (* 2 moon-anomaly) (* 2 moon-argument))))
331	(* -0.00003 (solar-sin-degrees (+ moon-anomaly sun-anomaly
332	(* 2 moon-argument))))
333	(* 0.00003 (solar-sin-degrees (- moon-anomaly sun-anomaly
334	(* -2 moon-argument))))
335	(* -0.00002 (solar-sin-degrees (- moon-anomaly sun-anomaly
336	(* 2 moon-argument))))
337	(* -0.00002 (solar-sin-degrees
338	(+ (* 3 moon-anomaly) sun-anomaly)))
339	(* 0.00002 (solar-sin-degrees (* 4 moon-anomaly)))))
340	(additional
341	(+ (* 0.000325 (solar-sin-degrees A1))
342	(* 0.000165 (solar-sin-degrees A2))
343	(* 0.000164 (solar-sin-degrees A3))
344	(* 0.000126 (solar-sin-degrees A4))
345	(* 0.000110 (solar-sin-degrees A5))
346	(* 0.000062 (solar-sin-degrees A6))
347	(* 0.000060 (solar-sin-degrees A7))
348	(* 0.000056 (solar-sin-degrees A8))
349	(* 0.000047 (solar-sin-degrees A9))
350	(* 0.000042 (solar-sin-degrees A10))
351	(* 0.000040 (solar-sin-degrees A11))
352	(* 0.000037 (solar-sin-degrees A12))
353	(* 0.000035 (solar-sin-degrees A13))
354	(* 0.000023 (solar-sin-degrees A14))))
355	(newJDE (+ JDE correction additional)))
356	(+ newJDE
357	(- (solar-ephemeris-correction
358	(extract-calendar-year
359	(calendar-gregorian-from-absolute
360	(floor (calendar-absolute-from-astro newJDE))))))
361	(/ calendar-time-zone 60.0 24.0))))
362
363	(defun lunar-new-moon-on-or-after (d)
364	"Astronomical (Julian) day number of first new moon on or after astronomical
365	(Julian) day number d. The fractional part is the time of day.
366
367	The date and time are local time, including any daylight savings rules,
368	as governed by the values of calendar-daylight-savings-starts,
369	calendar-daylight-savings-starts-time, calendar-daylight-savings-ends,
370	calendar-daylight-savings-ends-time, calendar-daylight-time-offset, and
371	calendar-time-zone."
372	(let* ((date (calendar-gregorian-from-absolute
373	(floor (calendar-absolute-from-astro d))))
374	(year (+ (extract-calendar-year date)
375	(/ (calendar-day-number date) 365.25)))
376	(k (floor (* (- year 2000.0) 12.3685)))
377	(date (lunar-new-moon-time k)))
378	(while (< date d)
379	(setq k (1+ k))
380	(setq date (lunar-new-moon-time k)))
381	(let* ((a-date (calendar-absolute-from-astro date))
382	(time (* 24 (- a-date (truncate a-date))))
383	(date (calendar-gregorian-from-absolute (truncate a-date)))
384	(adj (dst-adjust-time date time)))
385	(calendar-astro-from-absolute
386	(+ (calendar-absolute-from-gregorian (car adj))
387	(/ (car (cdr adj)) 24.0))))))
388
7e1dae73 JB	389	(provide 'lunar)
	390
	391	;;; lunar.el ends here