[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., 51 Franklin Street, Fifth Floor,
;; Boston, MA 02110-1301, 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: The Millennium Edition'' by Edward M. Reingold
;; and Nachum Dershowitz, Cambridge University Press (2001).

;; 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:

(defvar date)
(defvar displayed-month)
(defvar displayed-year)

(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 (&optional mark)
"Moon phases diary entry.

An optional parameter MARK specifies a face or single-character string to
use when highlighting the day in the calendar."
  (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)
        (cons mark (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)

;;; arch-tag: 72f0b8a4-7bcc-4a1b-b67a-ff53c4a1d222
;;; lunar.el ends here
Commit	Line	Data
3afbc435	1	;;; lunar.el --- calendar functions for phases of the moon
7e1dae73	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	22	;; along with GNU Emacs; see the file COPYING. If not, write to the
3a35cf56 LK	23	;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
3a35cf56 LK	24	;; Boston, MA 02110-1301, 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	40	;; Technical details of all the calendrical calculations can be found in
fffaba77 PE	41	;; ``Calendrical Calculations: The Millennium Edition'' by Edward M. Reingold
fffaba77 PE	42	;; and Nachum Dershowitz, Cambridge University Press (2001).
a96a5fca	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
04ec3414	52	(defvar date)
0b0f8fa4 GM	53	(defvar displayed-month)
	54	(defvar displayed-year)
	55
7e1dae73 JB	56	(if (fboundp 'atan)
7e1dae73 JB	57	(require 'lisp-float-type)
3afbc435	58	(error "Lunar calculations impossible since floating point is unavailable"))
7e1dae73 JB	59
	60	(require 'solar)
	61
	62	(defun lunar-phase-list (month year)
	63	"List of lunar phases for three months starting with Gregorian MONTH, YEAR."
	64	(let ((end-month month)
	65	(end-year year)
	66	(start-month month)
	67	(start-year year))
	68	(increment-calendar-month end-month end-year 3)
	69	(increment-calendar-month start-month start-year -1)
	70	(let* ((end-date (list (list end-month 1 end-year)))
a1506d29	71	(start-date (list (list start-month
7e1dae73 JB	72	(calendar-last-day-of-month
	73	start-month start-year)
	74	start-year)))
	75	(index (* 4
	76	(truncate
	77	(* 12.3685
	78	(+ year
	79	( / (calendar-day-number (list month 1 year))
	80	366.0)
	81	-1900)))))
	82	(new-moon (lunar-phase index))
	83	(list))
	84	(while (calendar-date-compare new-moon end-date)
	85	(if (calendar-date-compare start-date new-moon)
	86	(setq list (append list (list new-moon))))
	87	(setq index (1+ index))
	88	(setq new-moon (lunar-phase index)))
	89	list)))
	90
	91	(defun lunar-phase (index)
	92	"Local date and time of lunar phase INDEX.
	93	Integer below INDEX/4 gives the lunation number, counting from Jan 1, 1900;
	94	remainder mod 4 gives the phase: 0 new moon, 1 first quarter, 2 full moon,
	95	3 last quarter."
b6c0aabf	96	(let* ((phase (mod index 4))
7e1dae73 JB	97	(index (/ index 4.0))
	98	(time (/ index 1236.85))
	99	(date (+ (calendar-absolute-from-gregorian '(1 0.5 1900))
	100	0.75933
	101	(* 29.53058868 index)
	102	(* 0.0001178 time time)
	103	(* -0.000000155 time time time)
	104	(* 0.00033
	105	(solar-sin-degrees (+ 166.56
	106	(* 132.87 time)
	107	(* -0.009173 time time))))))
e7bb3aeb	108	(sun-anomaly (mod
7e1dae73 JB	109	(+ 359.2242
	110	(* 29.105356 index)
	111	(* -0.0000333 time time)
	112	(* -0.00000347 time time time))
	113	360.0))
e7bb3aeb	114	(moon-anomaly (mod
7e1dae73 JB	115	(+ 306.0253
	116	(* 385.81691806 index)
	117	(* 0.0107306 time time)
	118	(* 0.00001236 time time time))
	119	360.0))
e7bb3aeb	120	(moon-lat (mod
7e1dae73 JB	121	(+ 21.2964
	122	(* 390.67050646 index)
	123	(* -0.0016528 time time)
	124	(* -0.00000239 time time time))
	125	360.0))
	126	(adjustment
	127	(if (memq phase '(0 2))
	128	(+ (* (- 0.1734 (* 0.000393 time))
	129	(solar-sin-degrees sun-anomaly))
	130	(* 0.0021 (solar-sin-degrees (* 2 sun-anomaly)))
	131	(* -0.4068 (solar-sin-degrees moon-anomaly))
	132	(* 0.0161 (solar-sin-degrees (* 2 moon-anomaly)))
	133	(* -0.0004 (solar-sin-degrees (* 3 moon-anomaly)))
	134	(* 0.0104 (solar-sin-degrees (* 2 moon-lat)))
	135	(* -0.0051 (solar-sin-degrees (+ sun-anomaly moon-anomaly)))
	136	(* -0.0074 (solar-sin-degrees (- sun-anomaly moon-anomaly)))
	137	(* 0.0004 (solar-sin-degrees (+ (* 2 moon-lat) sun-anomaly)))
	138	(* -0.0004 (solar-sin-degrees (- (* 2 moon-lat) sun-anomaly)))
	139	(* -0.0006 (solar-sin-degrees
	140	(+ (* 2 moon-lat) moon-anomaly)))
	141	(* 0.0010 (solar-sin-degrees (- (* 2 moon-lat) moon-anomaly)))
	142	(* 0.0005 (solar-sin-degrees
	143	(+ (* 2 moon-anomaly) sun-anomaly))))
	144	(+ (* (- 0.1721 (* 0.0004 time))
	145	(solar-sin-degrees sun-anomaly))
	146	(* 0.0021 (solar-sin-degrees (* 2 sun-anomaly)))
	147	(* -0.6280 (solar-sin-degrees moon-anomaly))
	148	(* 0.0089 (solar-sin-degrees (* 2 moon-anomaly)))
	149	(* -0.0004 (solar-sin-degrees (* 3 moon-anomaly)))
	150	(* 0.0079 (solar-sin-degrees (* 2 moon-lat)))
	151	(* -0.0119 (solar-sin-degrees (+ sun-anomaly moon-anomaly)))
	152	(* -0.0047 (solar-sin-degrees (- sun-anomaly moon-anomaly)))
	153	(* 0.0003 (solar-sin-degrees (+ (* 2 moon-lat) sun-anomaly)))
	154	(* -0.0004 (solar-sin-degrees (- (* 2 moon-lat) sun-anomaly)))
	155	(* -0.0006 (solar-sin-degrees (+ (* 2 moon-lat) moon-anomaly)))
	156	(* 0.0021 (solar-sin-degrees (- (* 2 moon-lat) moon-anomaly)))
	157	(* 0.0003 (solar-sin-degrees
	158	(+ (* 2 moon-anomaly) sun-anomaly)))
	159	(* 0.0004 (solar-sin-degrees
	160	(- sun-anomaly (* 2 moon-anomaly))))
	161	(* -0.0003 (solar-sin-degrees
	162	(+ (* 2 sun-anomaly) moon-anomaly))))))
	163	(adj (+ 0.0028
	164	(* -0.0004 (solar-cosine-degrees
	165	sun-anomaly))
	166	(* 0.0003 (solar-cosine-degrees
	167	moon-anomaly))))
	168	(adjustment (cond ((= phase 1) (+ adjustment adj))
	169	((= phase 2) (- adjustment adj))
	170	(t adjustment)))
	171	(date (+ date adjustment))
238c5cc1 PE	172	(date (+ date (/ (- calendar-time-zone
238c5cc1 PE	173	(solar-ephemeris-correction
80e48f9f JB	174	(extract-calendar-year
80e48f9f JB	175	(calendar-gregorian-from-absolute
238c5cc1 PE	176	(truncate date)))))
238c5cc1 PE	177	60.0 24.0)))
7e1dae73	178	(time (* 24 (- date (truncate date))))
e483c805	179	(date (calendar-gregorian-from-absolute (truncate date)))
8a45b040	180	(adj (dst-adjust-time date time)))
e483c805	181	(list (car adj) (apply 'solar-time-string (cdr adj)) phase)))
7e1dae73 JB	182
	183	(defun lunar-phase-name (phase)
	184	"Name of lunar PHASE.
	185	0 = new moon, 1 = first quarter, 2 = full moon, 3 = last quarter."
	186	(cond ((= 0 phase) "New Moon")
	187	((= 1 phase) "First Quarter Moon")
	188	((= 2 phase) "Full Moon")
	189	((= 3 phase) "Last Quarter Moon")))
	190
	191	(defun calendar-phases-of-moon ()
	192	"Create a buffer with the lunar phases for the current calendar window."
	193	(interactive)
	194	(message "Computing phases of the moon...")
	195	(let ((m1 displayed-month)
	196	(y1 displayed-year)
	197	(m2 displayed-month)
cc4879d2	198	(y2 displayed-year))
7e1dae73 JB	199	(increment-calendar-month m1 y1 -1)
	200	(increment-calendar-month m2 y2 1)
	201	(set-buffer (get-buffer-create lunar-phases-buffer))
	202	(setq buffer-read-only nil)
	203	(calendar-set-mode-line
1a380827 RS	204	(if (= y1 y2)
	205	(format "Phases of the Moon from %s to %s, %d%%-"
	206	(calendar-month-name m1) (calendar-month-name m2) y2)
	207	(format "Phases of the Moon from %s, %d to %s, %d%%-"
	208	(calendar-month-name m1) y1 (calendar-month-name m2) y2)))
7e1dae73 JB	209	(erase-buffer)
	210	(insert
	211	(mapconcat
	212	'(lambda (x)
	213	(let ((date (car x))
	214	(time (car (cdr x)))
	215	(phase (car (cdr (cdr x)))))
	216	(concat (calendar-date-string date)
	217	": "
	218	(lunar-phase-name phase)
	219	" "
	220	time)))
	221	(lunar-phase-list m1 y1) "\n"))
	222	(goto-char (point-min))
	223	(set-buffer-modified-p nil)
	224	(setq buffer-read-only t)
	225	(display-buffer lunar-phases-buffer)
	226	(message "Computing phases of the moon...done")))
	227
	228	;;;###autoload
	229	(defun phases-of-moon (&optional arg)
	230	"Display the quarters of the moon for last month, this month, and next month.
	231	If called with an optional prefix argument, prompts for month and year.
	232
	233	This function is suitable for execution in a .emacs file."
	234	(interactive "P")
	235	(save-excursion
46124264	236	(let* ((date (if arg
cc4879d2 ER	237	(calendar-read-date t)
	238	(calendar-current-date)))
	239	(displayed-month (extract-calendar-month date))
	240	(displayed-year (extract-calendar-year date)))
7e1dae73 JB	241	(calendar-phases-of-moon))))
7e1dae73 JB	242
e0ab9b68 RS	243	(defun diary-phases-of-moon (&optional mark)
	244	"Moon phases diary entry.
	245
a1506d29	246	An optional parameter MARK specifies a face or single-character string to
e0ab9b68	247	use when highlighting the day in the calendar."
7e1dae73 JB	248	(let* ((index (* 4
	249	(truncate
	250	(* 12.3685
	251	(+ (extract-calendar-year date)
	252	( / (calendar-day-number date)
	253	366.0)
	254	-1900)))))
	255	(phase (lunar-phase index)))
	256	(while (calendar-date-compare phase (list date))
	257	(setq index (1+ index))
	258	(setq phase (lunar-phase index)))
	259	(if (calendar-date-equal (car phase) date)
e0ab9b68 RS	260	(cons mark (concat (lunar-phase-name (car (cdr (cdr phase)))) " "
e0ab9b68 RS	261	(car (cdr phase)))))))
7e1dae73	262
8a45b040 ER	263
	264	;; For the Chinese calendar the calculations for the new moon need to be more
	265	;; accurate than those above, so we use more terms in the approximation.
	266
	267	(defun lunar-new-moon-time (k)
	268	"Astronomical (Julian) day number of K th new moon."
	269	(let* ((T (/ k 1236.85))
	270	(T2 (* T T))
	271	(T3 (* T T T))
	272	(T4 (* T2 T2))
	273	(JDE (+ 2451550.09765
	274	(* 29.530588853 k)
	275	(* 0.0001337 T2)
	276	(* -0.000000150 T3)
	277	(* 0.00000000073 T4)))
	278	(E (- 1 (* 0.002516 T) (* 0.0000074 T2)))
	279	(sun-anomaly (+ 2.5534
	280	(* 29.10535669 k)
	281	(* -0.0000218 T2)
	282	(* -0.00000011 T3)))
	283	(moon-anomaly (+ 201.5643
	284	(* 385.81693528 k)
	285	(* 0.0107438 T2)
	286	(* 0.00001239 T3)
	287	(* -0.000000058 T4)))
	288	(moon-argument (+ 160.7108
	289	(* 390.67050274 k)
	290	(* -0.0016341 T2)
	291	(* -0.00000227 T3)
	292	(* 0.000000011 T4)))
	293	(omega (+ 124.7746
	294	(* -1.56375580 k)
	295	(* 0.0020691 T2)
	296	(* 0.00000215 T3)))
	297	(A1 (+ 299.77 (* 0.107408 k) (* -0.009173 T2)))
	298	(A2 (+ 251.88 (* 0.016321 k)))
	299	(A3 (+ 251.83 (* 26.641886 k)))
	300	(A4 (+ 349.42 (* 36.412478 k)))
	301	(A5 (+ 84.66 (* 18.206239 k)))
	302	(A6 (+ 141.74 (* 53.303771 k)))
	303	(A7 (+ 207.14 (* 2.453732 k)))
	304	(A8 (+ 154.84 (* 7.306860 k)))
	305	(A9 (+ 34.52 (* 27.261239 k)))
	306	(A10 (+ 207.19 (* 0.121824 k)))
	307	(A11 (+ 291.34 (* 1.844379 k)))
	308	(A12 (+ 161.72 (* 24.198154 k)))
	309	(A13 (+ 239.56 (* 25.513099 k)))
	310	(A14 (+ 331.55 (* 3.592518 k)))
	311	(correction
	312	(+ (* -0.40720 (solar-sin-degrees moon-anomaly))
	313	(* 0.17241 E (solar-sin-degrees sun-anomaly))
	314	(* 0.01608 (solar-sin-degrees (* 2 moon-anomaly)))
	315	(* 0.01039 (solar-sin-degrees (* 2 moon-argument)))
	316	(* 0.00739 E (solar-sin-degrees (- moon-anomaly sun-anomaly)))
	317	(* -0.00514 E (solar-sin-degrees (+ moon-anomaly sun-anomaly)))
	318	(* 0.00208 E E (solar-sin-degrees (* 2 sun-anomaly)))
	319	(* -0.00111 (solar-sin-degrees
	320	(- moon-anomaly (* 2 moon-argument))))
	321	(* -0.00057 (solar-sin-degrees
	322	(+ moon-anomaly (* 2 moon-argument))))
	323	(* 0.00056 E (solar-sin-degrees
	324	(+ (* 2 moon-anomaly) sun-anomaly)))
	325	(* -0.00042 (solar-sin-degrees (* 3 moon-anomaly)))
	326	(* 0.00042 E (solar-sin-degrees
327	(+ sun-anomaly (* 2 moon-argument))))
328	(* 0.00038 E (solar-sin-degrees
329	(- sun-anomaly (* 2 moon-argument))))
330	(* -0.00024 E (solar-sin-degrees
331	(- (* 2 moon-anomaly) sun-anomaly)))
332	(* -0.00017 (solar-sin-degrees omega))
333	(* -0.00007 (solar-sin-degrees
334	(+ moon-anomaly (* 2 sun-anomaly))))
335	(* 0.00004 (solar-sin-degrees
336	(- (* 2 moon-anomaly) (* 2 moon-argument))))
337	(* 0.00004 (solar-sin-degrees (* 3 sun-anomaly)))
338	(* 0.00003 (solar-sin-degrees (+ moon-anomaly sun-anomaly
339	(* -2 moon-argument))))
340	(* 0.00003 (solar-sin-degrees
341	(+ (* 2 moon-anomaly) (* 2 moon-argument))))
342	(* -0.00003 (solar-sin-degrees (+ moon-anomaly sun-anomaly
343	(* 2 moon-argument))))
344	(* 0.00003 (solar-sin-degrees (- moon-anomaly sun-anomaly
345	(* -2 moon-argument))))
346	(* -0.00002 (solar-sin-degrees (- moon-anomaly sun-anomaly
347	(* 2 moon-argument))))
348	(* -0.00002 (solar-sin-degrees
349	(+ (* 3 moon-anomaly) sun-anomaly)))
350	(* 0.00002 (solar-sin-degrees (* 4 moon-anomaly)))))
351	(additional
352	(+ (* 0.000325 (solar-sin-degrees A1))
353	(* 0.000165 (solar-sin-degrees A2))
354	(* 0.000164 (solar-sin-degrees A3))
355	(* 0.000126 (solar-sin-degrees A4))
356	(* 0.000110 (solar-sin-degrees A5))
357	(* 0.000062 (solar-sin-degrees A6))
358	(* 0.000060 (solar-sin-degrees A7))
359	(* 0.000056 (solar-sin-degrees A8))
360	(* 0.000047 (solar-sin-degrees A9))
361	(* 0.000042 (solar-sin-degrees A10))
362	(* 0.000040 (solar-sin-degrees A11))
363	(* 0.000037 (solar-sin-degrees A12))
364	(* 0.000035 (solar-sin-degrees A13))
365	(* 0.000023 (solar-sin-degrees A14))))
366	(newJDE (+ JDE correction additional)))
367	(+ newJDE
368	(- (solar-ephemeris-correction
369	(extract-calendar-year
370	(calendar-gregorian-from-absolute
371	(floor (calendar-absolute-from-astro newJDE))))))
372	(/ calendar-time-zone 60.0 24.0))))
373
374	(defun lunar-new-moon-on-or-after (d)
375	"Astronomical (Julian) day number of first new moon on or after astronomical
3001419f	376	\(Julian) day number d. The fractional part is the time of day.
8a45b040 ER	377
	378	The date and time are local time, including any daylight savings rules,
	379	as governed by the values of calendar-daylight-savings-starts,
	380	calendar-daylight-savings-starts-time, calendar-daylight-savings-ends,
	381	calendar-daylight-savings-ends-time, calendar-daylight-time-offset, and
	382	calendar-time-zone."
	383	(let* ((date (calendar-gregorian-from-absolute
	384	(floor (calendar-absolute-from-astro d))))
	385	(year (+ (extract-calendar-year date)
	386	(/ (calendar-day-number date) 365.25)))
	387	(k (floor (* (- year 2000.0) 12.3685)))
	388	(date (lunar-new-moon-time k)))
	389	(while (< date d)
	390	(setq k (1+ k))
	391	(setq date (lunar-new-moon-time k)))
	392	(let* ((a-date (calendar-absolute-from-astro date))
	393	(time (* 24 (- a-date (truncate a-date))))
	394	(date (calendar-gregorian-from-absolute (truncate a-date)))
	395	(adj (dst-adjust-time date time)))
	396	(calendar-astro-from-absolute
	397	(+ (calendar-absolute-from-gregorian (car adj))
	398	(/ (car (cdr adj)) 24.0))))))
	399
7e1dae73 JB	400	(provide 'lunar)
7e1dae73 JB	401
ab5796a9	402	;;; arch-tag: 72f0b8a4-7bcc-4a1b-b67a-ff53c4a1d222
7e1dae73	403	;;; lunar.el ends here