The Sun's Altitude

This instrument is a plinth. It was described by Claudius Ptolemy in the second century A.D. and was used to measure the maximum altitude of the Sun above the horizon. At noon, at the highest point of its trajectory, the Sun crosses the meridian of the place of observation.
Módulo para saber la altura a la que se encuentra el Sol según la latitud

This altitude depends on the latitude, and also varies throughout the year; maximum altitude occurs during the summer solstice and the minimum altitude occurs during the winter solstice. At the latitude of Valencia, the maximum altitude reached by the Sun during summer solstice is 73º 57’; during the winter solstice it only reaches 27º 5’.


If you look at the shadow of the indicator rod at 12:00 solar time, you can obtain the solar declination for today's date. The declination is the angle between the Sun and the celestial equator. As the declination of the sun varies according to the day of the year, the plinth can also be used as an accurate annual calendar –but only at exactly solar noon.


The plinth can be used to determine when the solstices and equinoxes will occur. To do so, all you need to do is read off the mark indicated by the shadow at solar noon.