How to calculate sun position?

[LeoSantaCruz]

Try this one instead:

Code:

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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

Where can i get the License for this code?

[Erwin van der Zwart]

Hi,

You don't need a license, it's just a mathematical function..

BR,

Erwin

[LeoSantaCruz]

Hi,

You don't need a license, it's just a mathematical function..

BR,

Erwin

So I can just Reference to this site? I am asking because i am using this function for a Project.

[admin]

Original JavaScript code is under BSD license: https://github.com/mourner/suncalc

[Trond Hoyem]

Try this one instead:

Code:

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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

I have used this for a few different applications on SL, and it works. But today I implementet this on a LM5, and i get all wrong values from it.

When I log the returned values I get; 

* arg: 1
  * number: 383
* arg: 2
  * number: 1112

Any ideas why? I even tested to enter it at the SL I use for testing at my office, and then I get the correct values.
The firmware of the LM5 is 20180822.

[Daniel]

do you have time set correctly in LM ?

[Trond Hoyem]

do you have time set correctly in LM ?

Yes, first thing I checked.

But anyway, the values should still be within 360 degrees, as that would be the highest possible Azimuth, and highest possible Elevation should be 90 degrees.

[Daniel]

Post your full script I will check on both devices but there can't be any difference

[Trond Hoyem]

Post your full script I will check on both devices but there can't be any difference

I disabled the script, and then enabled it again, and now it works....

[Erwin van der Zwart]

Try this one instead:

Code:

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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

Hi Admin,

On what calculation is suncalc (above) based? The Azimuth is 28 degrees wrong, i just tested function suncalc vs sunposition and these are the results:

log(suncalc(52.5167747, 6.0830219, os.time()) )

log(sunposition(52.5167747, 6.0830219, os.time()) )

Suncalc 02.07.2020 14:21:25
* arg: 1 Altitude
  * number: 59.4576360078012
* arg: 2 Azimuth
  * number: 198.878804294899

Sunposition 02.07.2020 14:21:25
* arg: 1 Altitude
  * number: 59.3596373934031
* arg: 2 Azimuth
  * number: 160.948315437194 


Any idea what might be wrong in the function suncalc?

BR,

Erwin

[admin]

Hi Erwin, looks like the sunpositon function is wrong. I've checked several online calculators and they give a result similar to what suncalc produces. Suncalc formulas are taken from here: https://github.com/mourner/suncalc