Tilt of the Earth during the summer and winter solstice relative to the plane of the ecliptic. March 20 or 21 marks the arrival of the spring or vernal equinox when once again the poles are not tilted toward the sun. Day lengths on both of these days, regardless of latitude, are exactly 12 hours. Tilt of the Earth during the vernal and autumnal equinox relative to the plane of the ecliptic. The following table describes the changes in solar altitude at solar noon for the two solstices and equinoxes.
Maximum sun altitudes for selected latitudes during the two solstices and equinoxes.
The following links show graphical illustrations of the annual movements of the sun in our skies for selected latitudes. In these illustrations, solar angles are measured from both true north and true south for solar noon . In this equation, L is the latitude of the location in degrees and D is the declination. All answers from this equation are given relative to true north for southern latitudes and true south for northern latitudes. For our purposes only the declinations of the two solstices and two equinoxes are important.