I did some research on the calculation of the declination (the difference between the angle of the sun and the latitude). I found approximations for that value. Based on that information I wrote the following function for StarOffice:<br><br>Function Declination (cd)<br> ref= datevalue ("1.1."+year(cd))<br> longitude = 0<br> t = cd -ref + 1 + (12 - longitude / 15 ) / 24<br> M = (0.9856 * t - 3.289)<br> L = (M + 1.916 * sin((M*Pi/180)) + 0.02 * sin((2 * M)*Pi/180) + 282.634)<br> sindec = 0.39782 * sin(L*Pi/180)<br> Declination = atn(sindec/sqr(1 - sindec^2))*180/PI<br> <br>End Function<br><br>cd is a date,<br>cd - ref is the the day of the year, <br>Declination is in degrees<br><br> I used the function to create a graph.