Is it sunrise or sunset with an offset?

[rocfusion]

Hi Pontus,

The when is an optional parameter,  so you you can then ask for the sunset \ sunrise for next Tuesday.    Your rscalc function is different to mine.  Here is mine which is from the Feb 2015 release of the firmware.

Thanks,

Roger

Code:

-- sunrise / sunset calculation
function rscalc(latitude, longitude, when)
 local pi = math.pi
 local doublepi = pi * 2
 local rads = pi / 180.0

 local TZ = function(when)
   local ts = os.time(when)
   local utcdate, localdate = os.date('!*t', ts), os.date('*t', ts)
   localdate.isdst = false

   local diff = os.time(localdate) - os.time(utcdate)
   return math.floor(diff / 3600)
 end

 local range = function(x)
   local a = x / doublepi
   local b = doublepi * (a - math.floor(a))
   return b < 0 and (doublepi + b) or b
 end

 when = when or os.date('*t')

 local y2k = { year = 2000, month = 1, day = 1 }
 local y2kdays = os.time(when) - os.time(y2k)
 y2kdays = math.ceil(y2kdays / 86400)

 local meanlongitude = range(280.461 * rads + 0.9856474 * rads * y2kdays)
 local meananomaly = range(357.528 * rads + 0.9856003 * rads * y2kdays)
 local lambda = range(meanlongitude + 1.915 * rads * math.sin(meananomaly) + rads / 50 * math.sin(2 * meananomaly))

 local obliq = 23.439 * rads - y2kdays * rads / 2500000

 local alpha = math.atan2(math.cos(obliq) * math.sin(lambda), math.cos(lambda))
 local declination = math.asin(math.sin(obliq) * math.sin(lambda))

 local LL = meanlongitude - alpha
 if meanlongitude < pi then
   LL = LL + doublepi
 end

 local dfo = pi / 216.45

 if latitude < 0 then
   dfo = -dfo
 end

 local fo = math.min(math.tan(declination + dfo) * math.tan(latitude * rads), 1)
 local ha = 12 * math.asin(fo) / pi + 6

 local timezone = TZ(when)
 local equation = 12 + timezone + 24 * (1 - LL / doublepi) - longitude / 15

 local sunrise, sunset = equation - ha, equation + ha

 if sunrise > 24 then
   sunrise = sunrise - 24
 end

 if sunset > 24 then
   sunset = sunset - 24
 end

 return math.floor(sunrise * 60), math.ceil(sunset * 60)
end