Below is a script that will calculate the solar azimuth and altitude (i.e. the position of the sun in the sky) and put the values in two virtual devices. These devices can then be used to determine whether to close blinds/shades, etc. I found the base code on the internet and have been running it here for a couple of days and seems to be relatively accurate (at least for my location). To use it, create two virtual devices (see screenshots below), and edit the script with the reference IDs of those devices and also your local lat/long. I run the script using a recurring event (every 5 minutes, but adjust to whatever you want for an update time). It's only been tested on Windows and may need some minor mods to work on linux.

Code:

'From c code posted here: http://www.psa.es/sdg/sunpos.htm 'VB.NET Conversion posted here: http://www.vbforums.com/showthread.php?832645-Solar-position-calculator 'converted for HomeSeer use by Sparkman v1.0 Imports System.Math Sub Main(ByVal Parms As String) Dim Debug As Boolean = False Dim logName As String = "Solar Position" Dim dLatitude As Double = [B]51.1[/B] Dim dLongitude As Double = [B]-115.1[/B] Dim hsAzimuthDevice As Integer = [B]1234[/B] Dim hsAltitudeDevice As Integer = [B]1235[/B] Dim pi As Double = 3.14159265358979 Dim rad As Double = pi / 180 Dim dEarthMeanRadius As Double = 6371.01 Dim dAstronomicalUnit As Double = 149597890 Dim iYear As Integer = DateTime.UtcNow.Year Dim iMonth As Integer = DateTime.UtcNow.Month Dim iDay As Integer = DateTime.UtcNow.Day Dim dHours As Double = DateTime.UtcNow.Hour Dim dMinutes As Double = DateTime.UtcNow.Minute Dim dSeconds As Double = DateTime.UtcNow.Second Dim dZenithAngle As Double Dim dZenithAngleParallax As Double Dim dAzimuth As Double Dim dAltitudeAngle As Double Dim dElapsedJulianDays As Double Dim dDecimalHours As Double Dim dEclipticLongitude As Double Dim dEclipticObliquity As Double Dim dRightAscension As Double Dim dDeclination As Double Dim dY As Double Dim dX As Double Dim dJulianDate As Double Dim liAux1 As Integer Dim liAux2 As Integer Dim dMeanLongitude As Double Dim dMeanAnomaly As Double Dim dOmega As Double Dim dSin_EclipticLongitude As Double Dim dGreenwichMeanSiderealTime As Double Dim dLocalMeanSiderealTime As Double Dim dLatitudeInRadians As Double Dim dHourAngle As Double Dim dCos_Latitude As Double Dim dSin_Latitude As Double Dim dCos_HourAngle As Double Dim dParallax As Double Try ' Calculate difference in days between the current Julian Day and JD 2451545.0, which is noon 1 January 2000 Universal Time ' Calculate time of the day in UT decimal hours dDecimalHours = dHours + (dMinutes + dSeconds / 60.0) / 60.0 ' Calculate current Julian Day liAux1 = (iMonth - 14) \ 12 liAux2 = (1461 * (iYear + 4800 + liAux1)) \ 4 + (367 * (iMonth - 2 - 12 * liAux1)) \ 12 - (3 * ((iYear + 4900 + liAux1) \ 100)) \ 4 + iDay - 32075 dJulianDate = CDbl(liAux2) - 0.5 + dDecimalHours / 24.0 ' Calculate difference between current Julian Day and JD 2451545.0 dElapsedJulianDays = dJulianDate - 2451545.0 If Debug Then hs.writelog(logName,"Elapsed Julian Days Since 2000/01/01: " & CStr(dElapsedJulianDays)) ' Calculate ecliptic coordinates (ecliptic longitude and obliquity of the ecliptic in radians but without limiting the angle to be less than 2*Pi ' (i.e., the result may be greater than 2*Pi) dOmega = 2.1429 - 0.0010394594 * dElapsedJulianDays dMeanLongitude = 4.895063 + 0.017202791698 * dElapsedJulianDays ' Radians dMeanAnomaly = 6.24006 + 0.0172019699 * dElapsedJulianDays dEclipticLongitude = dMeanLongitude + 0.03341607 * Math.Sin(dMeanAnomaly) + 0.00034894 * Math.Sin(2 * dMeanAnomaly) - 0.0001134 - 0.0000203 * Math.Sin(dOmega) dEclipticObliquity = 0.4090928 - 0.000000006214 * dElapsedJulianDays + 0.0000396 * Math.Cos(dOmega) If Debug Then hs.writelog(logName,"Ecliptic Longitude: " & CStr(dEclipticLongitude)) If Debug Then hs.writelog(logName,"Ecliptic Obliquity: " & CStr(dEclipticObliquity)) ' Calculate celestial coordinates ( right ascension and declination ) in radians but without limiting the angle to be less than 2*Pi (i.e., the result may be greater than 2*Pi) dSin_EclipticLongitude = Math.Sin(dEclipticLongitude) dY = Math.Cos(dEclipticObliquity) * dSin_EclipticLongitude dX = Math.Cos(dEclipticLongitude) dRightAscension = Math.Atan2(dY, dX) If dRightAscension < 0.0 Then dRightAscension = dRightAscension + (2 * pi) End If dDeclination = Math.Asin(Math.Sin(dEclipticObliquity) * dSin_EclipticLongitude) If Debug Then hs.writelog(logName,"Declination: " & CStr(dDeclination)) ' Calculate local coordinates ( azimuth and zenith angle ) in degrees dGreenwichMeanSiderealTime = 6.6974243242 + 0.0657098283 * dElapsedJulianDays + dDecimalHours dLocalMeanSiderealTime = (dGreenwichMeanSiderealTime * 15 + dLongitude) * rad dHourAngle = dLocalMeanSiderealTime - dRightAscension If Debug Then hs.writelog(logName,"Hour Angle: " & CStr(dHourAngle)) dLatitudeInRadians = dLatitude * rad dCos_Latitude = Math.Cos(dLatitudeInRadians) dSin_Latitude = Math.Sin(dLatitudeInRadians) dCos_HourAngle = Math.Cos(dHourAngle) dZenithAngle = (Math.Acos(dCos_Latitude * dCos_HourAngle * Math.Cos(dDeclination) + Math.Sin(dDeclination) * dSin_Latitude)) dY = -Math.Sin(dHourAngle) dX = Math.Tan(dDeclination) * dCos_Latitude - dSin_Latitude * dCos_HourAngle dAzimuth = Math.Atan2(dY, dX) If dAzimuth < 0.0 Then dAzimuth = dAzimuth + (2 * pi) End If dAzimuth = dAzimuth / rad If Debug Then hs.writelog(logName,"Azimuth: " & CStr(dAzimuth)) hs.setdevicevaluebyref(hsAzimuthDevice,dAzimuth,True) ' Parallax Correction dParallax = (dEarthMeanRadius / dAstronomicalUnit) * Math.Sin(dZenithAngle) dZenithAngleParallax = (dZenithAngle + dParallax) / rad dAltitudeAngle = (dZenithAngleParallax * -1) + 90 If Debug Then hs.writelog(logName,"Altitude Angle: " & CStr(dAltitudeAngle)) hs.setdevicevaluebyref(hsAltitudeDevice,dAltitudeAngle,True) Catch ex As Exception hs.WriteLog(logName, "Exception " & ex.ToString) End Try End Sub

## Comment