created by Carl Sabanski
The Sun Charts illustrated on this page were created using an on-line program at the web site of the University of Oregon Solar Radiation Monitoring Laboratory. If you would like a set of Sun Charts for your location please visit their Sun Chart Program web page at: http://solardat.uoregon.edu/SunChartProgram.html
If you have ever had an interest in solar energy you have probably seen a sun chart. The sun chart enables you to locate the position of the sun at any time of day, during any month and for any location. It is a plot of the sun's altitude versus azimuth at different times throughout a given day. This is the sun's path for that day. This can be done for any day of the year. A sun chart will have plots for the sun's path for a particular day each month. If the times of day on each sun path are connected lines will be drawn that represent the hours of the day. A new sun chart is required to illustrate the sun's path at different latitudes.
Figure 1 is an example of a sun chart for latitude 50º N.
Figure 1: Sun Charts - Solar Time
A separate sun chart is generated for each half of the year. The sun's azimuth is varies from 0º to 360º and its elevation from 0º to 90º. The sun's path for a particular day each month is shown in blue and the lines for the hours of the day are in red. The time is local apparent time or solar time. Sun charts can also be created that show clock time and the hour lines are shifted for longitude correction and each hour line will show half the analemma. This can be seen in Figure 2 for a longitude of 95º W.
Figure 2: Sun Charts - Clock Time
Sun charts normally only show time lines for the full hours. Even so, a lot of useful information can be obtained from sun charts for sundial design. Figure 3 illustrates this.
Figure 3: Sun Chart Sundial Data
Figure 3 is the sun chart for a location at a latitude of 50º in the Northern Hemisphere. It should be noted that the sun charts for the Northern Hemisphere have a solar azimuth range of 0º to 360º. The sun charts for the Southern Hemisphere have a solar azimuth range of -180º to 180º. Note that the sun is due east at a solar azimuth of 90º for both the Northern and Southern Hemispheres and due west at 270º for the Northern Hemisphere and -90º for the Southern Hemisphere.
The following dialling data can be obtained from the sun chart:
It is also possible to get the time range for a vertical declining sundial. This is a vertical sundial that is turned east or west of due south. As an example take a vertical sundial that declines15º east. The time range for this sundial will be those times associated with the solar azimuths of 75º and 255º in Figure 3.
It is also possible to obtain a polar sun path chart. Figure 4 is an example of a polar sun chart for latitude 50º N.
Figure 4: Polar Sun Chart - Solar Time
Take a look at the next two figures. These are sun charts for the Arctic Circle, 66º 33' 21" N, and the Antarctic Circle, 66º 33' 21" S. The sun reaches a maximum elevation at the summer solstice of: (90º - 66.56º) + 23.44º = 46.88º
Figure 5: Sun Chart for the Arctic Circle
Figure 6: Sun Chart for the Antarctic Circle
On the day of the Summer Solstice for the Northern and Southern Hemispheres, the sun is above the horizon a full 24 hours. The sun is due east at approximately 6:45 a.m. and due west at approximately 5:15 p.m. This means that a vertical direct south sundial at the Arctic Circle and a vertical direct north sundial at the Antarctic Circle will have the sun shining on them for approximately 10.5 hours. The interesting thing though is that a vertical direct north sundial at the Arctic Circle and a vertical direct south sundial at the Antarctic Circle will have the sun shining on them for approximately 13.5 hours.
As you can see, sun charts can provide some very interesting information.
If you are interested in seeing sun charts for the Equator and the North (South) Pole then continue on to: