How to calculate sun position?

[Auzzii]

Try this one instead:

Code:

function suncalc(lat, lng, time)
 -- sun calculations are based on http://aa.quae.nl/en/reken/zonpositie.html formulas
 local PI   = math.pi
 local sin  = math.sin
 local cos  = math.cos
 local tan  = math.tan
 local asin = math.asin
 local atan = math.atan2
 local acos = math.acos
 local deg  = math.deg
 local rad  = PI / 180
 local e = rad * 23.4397 -- obliquity of the Earth
 local daysec = 60 * 60 * 24
 local J1970 = 2440588
 local J2000 = 2451545

 local function toDays(time)
   return time / daysec - 0.5 + J1970 - J2000
 end

 local function rightAscension(l, b)
   return atan(sin(l) * cos(e) - tan(b) * sin(e), cos(l))
 end

 local function declination(l, b)
   return asin(sin(b) * cos(e) + cos(b) * sin(e) * sin(l))
 end

 local function azimuth(H, phi, dec)
   return atan(sin(H), cos(H) * sin(phi) - tan(dec) * cos(phi))
 end

 local function altitude(H, phi, dec)
   return asin(sin(phi) * sin(dec) + cos(phi) * cos(dec) * cos(H))
 end

 local function siderealTime(d, lw)
   return rad * (280.16 + 360.9856235 * d) - lw
 end

 local function astroRefraction(h)
   if h < 0 then -- the following formula works for positive altitudes only.
     h = 0 -- if h = -0.08901179 a div/0 would occur.
   end

   -- formula 16.4 of "Astronomical Algorithms" 2nd edition by Jean Meeus (Willmann-Bell, Richmond) 1998.
   -- 1.02 / tan(h + 10.26 / (h + 5.10)) h in degrees, result in arc minutes -> converted to rad:
   return 0.0002967 / math.tan(h + 0.00312536 / (h + 0.08901179))
 end

 -- general sun calculations
 local function solarMeanAnomaly(d)
   return rad * (357.5291 + 0.98560028 * d)
 end

 local function eclipticLongitude(M)
   local C = rad * (1.9148 * sin(M) + 0.02 * sin(2 * M) + 0.0003 * sin(3 * M)) -- equation of center
   local P = rad * 102.9372 -- perihelion of the Earth
   return M + C + P + PI
 end

 local function sunCoords(d)
   local M = solarMeanAnomaly(d)
   local L = eclipticLongitude(M)
   return declination(L, 0), rightAscension(L, 0)
 end

 local lw      = rad * -lng
 local phi     = rad * lat
 local d       = toDays(time or os.time())
 local dec, ra = sunCoords(d)
 local H       = siderealTime(d, lw) - ra

 local alt, az = altitude(H, phi, dec), azimuth(H, phi, dec)
 return deg(alt), 180 + deg(az)
end

Thanks. That one worked.

Trond

Hi,

Maybe someone have example code?

I need to get sun position every 5 min.
1) Elevation degree (0-100%)
2) Azimuth (0-360*)


thx