Make example sunrise-sunset script 12 times faster

examples/grand_canyon_daylight.py

@@ -1,17 +1,20 @@
+# Runtime was around 1 minute 4 seconds under the old find-discrete
+# regime; with the new find_risings() and find_settings() routines, this
+# script now takes around 5 seconds.  Nice.
+
 from skyfield.api import load, wgs84
 from skyfield import almanac
 
 ts = load.timescale()
 eph = load('de421.bsp')
 grand_canyon_village = wgs84.latlon(+36.0544, -112.1401)
+observer = eph['earth'] + grand_canyon_village
 tz_hours = -7
 start = ts.utc(1986, 1, 17, -tz_hours)
 #end = ts.utc(1987, 7, 14, -tz_hours)
 end = ts.utc(2022, 7, 14, -tz_hours)
-ss = almanac.sunrise_sunset(eph, grand_canyon_village)
-t, y = almanac.find_discrete(start, end, ss)
-sunrises = t[::2]
-sunsets = t[1::2]
+sunrises, _ = almanac.find_risings(observer, eph['Sun'], start, end)
+sunsets, _ = almanac.find_settings(observer, eph['Sun'], start, end)
 lengths = sunsets - sunrises
 print('date,hours_sunlight')
 for ti, length in zip(sunrises, lengths):