Interactive spreadsheet

Lat [°]
Long [°]


Mean Time [h]
Gmt Mer [°]
Azimuth [°]
Altitude [°]
Solar Time [h]
Sunrise [h]
Solar Noon [h]
Sunset [h]
Az Sunrise [°]
Alt Noon [°]
Az Sunset [°]
Day Length [h]
Timezone corr. [h]
Local EqT [h]



or Save data


Book associated with this spreadsheet

Solar Cookers

Cooking with the Sun - History, Theory, Construction, Recipes

An exhaustive manual-essay introducing you to the world of solar cookers that highlights the potential of these practical tools with which you can cook your dishes outdoors with solar energy alone. You will learn the history, development and refinement of solar cookers, but also the theory of apparent motion of the Sun, as well of solar radiation and its conversion into heat. This book is accompanied by an extensive theoretical and practical section that illustrates the working principles of solar cookers: complete with the methods to build them with recycled materials, illustrative examples and advice on recipes .


At the top of the spreadsheet, it is possible to vary all the parameters for the Sun position calculation (Lat, Long, Day, Month, Time, Gmt Mer) and, automatically, the results will be given in the bottom part: coordinates of the Sun, Day Length, Mean Time at sunrise and sunset, azimuth value of the Sun at sunset and sunrise, maximum altitude of the Sun during the day, i.e. at Solar Noon when Tv=12, Solar Time and Equation of Time of the day. Azimuth is measured from the south (Azimuth =0°) and is positive towards the west and negative towards the east.
This page allows the user to choose between decimal or sexagesimal notation for local coordinates, and performs automatic conversion. Gmt Mer is the longitude of the Timezone meridian and can be evaluated automatically when pressing button HERE or HERE&NOW for local calculation. To recover such data you must allow your device to access GPS. Daylight Saving Time is also evaluated automatically when pressing button NOW which recovers the current mean time. Time is expressed in the format h:m:s, where h stands for hours (0..23), m for minutes and s for seconds.
Note: for coordinates inserted by user, you should recover Gmt Mer and Daylight Saving Time as explained in my books. When firstly loaded, this webpage shows the coordinates of Murlo (SI, Italy), the day of the summer solstice, June 21, and Mean Time coinciding with the Solar Noon; some data evaluated are shown in the following table as an example:

Day Sunrise Tm time Sunrise Azimuth Solar Noon Tm time Sun Altitude at Solar Noon Sunset Tm time Sunset Azimuth
21 June 05:40:10 -123° 13:16:07 70.26° 20:52:03 123°
The fact that the azimuth of the sunset is 123°, i.e. greater than 90°, means that the position of the Sun at that moment is moved northwards.
Important: For simplicity, calculations made in this spreadsheet consider the Sun as a point, neglecting more detailed aspects such as the atmospheric refraction, the curvature of the Earth and the apparent diameter of the Sun.