diff options
Diffstat (limited to 'lisp/calendar/lunar.el')
| -rw-r--r-- | lisp/calendar/lunar.el | 27 |
1 files changed, 24 insertions, 3 deletions
diff --git a/lisp/calendar/lunar.el b/lisp/calendar/lunar.el index 616d2b0c4ed..3d5a0a236b4 100644 --- a/lisp/calendar/lunar.el +++ b/lisp/calendar/lunar.el @@ -91,6 +91,7 @@ remainder mod 4 gives the phase: 0 new moon, 1 first quarter, 2 full moon, (* -0.0016528 time time) (* -0.00000239 time time time)) 360.0)) + (eclipse (eclipse-check moon-lat phase)) (adjustment (if (memq phase '(0 2)) (+ (* (- 0.1734 (* 0.000393 time)) @@ -146,7 +147,26 @@ remainder mod 4 gives the phase: 0 new moon, 1 first quarter, 2 full moon, (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))) + (list (car adj) (apply 'solar-time-string (cdr adj)) phase eclipse))) + +;; from "Astronomy with your Personal Computer", Subroutine Eclipse +;; Line 7000 Peter Duffett-Smith Cambridge University Press 1990 +(defun eclipse-check (moon-lat phase) + (let* ((moon-lat (* (/ float-pi 180) moon-lat)) + (moon-lat (abs (- moon-lat (* (floor (/ moon-lat float-pi)) + float-pi)))) + (moon-lat (if (> moon-lat 0.37) + (- float-pi moon-lat) + moon-lat)) + (phase-name (cond ((= phase 0) "Solar") + ((= phase 2) "Lunar") + (t "")))) + (cond ((< moon-lat 2.42600766e-1) + (concat "** " phase-name " Eclipse **")) + ((< moon-lat 0.37) + (concat "** " phase-name " Eclipse possible **")) + (t + "")))) (defconst lunar-cycles-per-year 12.3685 ; 365.25/29.530588853 "Mean number of lunar cycles per 365.25 day year.") @@ -222,9 +242,10 @@ use instead of point." (insert (mapconcat (lambda (x) - (format "%s: %s %s" (calendar-date-string (car x)) + (format "%s: %s %s %s" (calendar-date-string (car x)) (lunar-phase-name (nth 2 x)) - (cadr x))) + (cadr x) + (car (last x)))) (lunar-phase-list m1 y1) "\n"))) (message "Computing phases of the moon...done")))) |