Watch Introductory Video

Using the Solar Visualizer Tool

Before you begin, use a compass or local map to find the east and west compass points. At each point, note the location of a distant object such as a tree or power pole. If you can't see far away, place a rock or other marker at the east and west compass points relative to where you will be standing.

Sunrise Solar Position

While holding the tool at arm's length and at eye level, align the center to the eastern compass point. Turn the tool until the SUNRISE line is level with the ground. If you can see the eastern horizon, the SUNRISE line should line up with the horizon.



The center of the tool is now aligned to the all-year average position of the Sun at 6:00 AM.  The analemma figure-8 loop shows you the exact position at 6:00 AM for each day of the year. This actual position is below the horizon in winter or above the horizon in summer.

If you're actually doing this at 6:00 AM (7:00 AM during Daylight Savings Time), the little circle in the analemma at today's date should coincide with the actual current Sun position.

Warning: To protect your eyes, never look at the Sun. Block direct sunlight from your eyes using the tool or your hands.

Sunset Solar Position

Now turn around and face west. While holding the tool at arm's length and at eye level, align the center to the western compass point, and turn the tool until the SUNSET line is level with the ground.



The center of the tool is now aligned to the average position of the Sun at 6:00 PM. The analemma shows the exact position of the Sun at 6:00 PM for each day of the year. Again, this is below the horizon in the winter or above it in summer.

If you're doing this at 6:00 PM (7:00 PM during Daylight Savings Time), the little circle at today's date should coincide with the actual Sun position.

Morning Solar Position

To find out where the Sun will be during the morning, go back to the 6:00 AM eastern SUNRISE point and align the tool to the horizon as before. The Sun moves in the direction of the red arrow by one arrow-length (15 cm or 6 inches) per hour.

To find the Sun's position at 7:00 AM, move the tool one full arrow-length. Keep the tool at arm's length, at a constant distance from your face.



Repeat these motions to see the Sun's position at 8:00 AM, 9:00 AM, and so on. Turn your whole body as needed to follow the motion of the tool.

When you reach the actual current time of day, the little circle at today's date should coincide with the actual Sun in the sky.

Warning: To protect your eyes, never look at the Sun. Block direct sunlight from your eyes using the tool or your hands.

If you do this at night, you'll see that the skinny end of the figure-8 analemma always points straight at Polaris, the North Star.

Noon Solar Position

At 12:00 noon, six arrow-lengths from the SUNRISE horizon, the Sun reaches its highest position in the sky, halfway between sunrise and sunset. At that point, the tool is directly south of you and positioned vertically, straight up from the southern horizon.



In the afternoon, you can work ether forward from noon or backward from the SUNSET horizon.

Afternoon and Evening Solar Position

To find the solar position late in the day, go back to the 6:00 PM western SUNSET point and align the tool to the horizon as before. Move the tool forward in the arrow direction by one arrow-length to see the solar position for 7:00 PM, then 8:00 PM, and so on; or backward by one arrow-length for 5:00 PM, then 4:00 PM, and so on.



Note: The SUNSET alignment to the horizon corresponds to 6 PM standard time or 7 PM Daylight Savings Time.

Tilt of the Tool Relative to the Horizon

The path of the red arrow through the sky is called the celestial equator, an imaginary line running from the eastern to the western compass point, tilted away from vertical by an angle equal to your latitude. The HelioTrak sundial shows this clearly.


For the house in the middle, the edge of the green circular plate is the horizon. The blue cage shows the path of the analemma as you move it through the sky from east to west. The cage's central circular path is the celestial equator. From the house, the horizon and celestial equator both appear as straight lines.

The tilt of the celestial equator depends on your latitude. You need to customize the tilt of the SUNRISE and SUNSET lines of the tool for your latitude, as described below.

How to Make the Solar Visualizer Tool

The HelioTrak solar position visualizer tool is free to print out for personal or educational use. These are the steps to make the tool.

1. Open the solar visualizer SVG file in a browser window.
   
   
2. Using your browser's File > Print command, print out the diagram at 100% full size, which requires 2 pages. Use a color printer if available; otherwise, black-and-white is fine.
   
   
   
   Some web browsers have trouble printing out the file at full size. My FireFox browser wouldn't print the second page, but Chrome worked fine. Set the printer margins to the minimum allowed, or manually set the margins to 0.0 of the left and right and 0.2 inches or 5 mm at the top and bottom.
   
   To check the printout for proper scale, verify that the distance between axis tick marks is 1.0 cm.
   
   
   
   
   
   
3. Trim off the margins from the ends of the sheets and tape them together to make a single long sheet.
   
   
   
   
4. Find the latitude of your location in degrees north or south by looking on a world map or by asking your smart device. 
   
   
5. Using a marker pen, draw two sets of diagonal lines, each slanted away from the long axis by an angle equal to your latitude. Use the faint 5-degree incremental markers as guides. The lines should form an "X" shape extending to the edges of the tool, as shown in the following latitude examples.
   
   
   
   55° North -- Moscow, Copenhagen, Edinburgh:
   
   
   40° North -- Beijing, Madrid, New York City:
   
   
   19° North -- Mumbai, Mexico City:
   
   
   0° North -- Equator, Kampala, Galapagos Islands:
   
   
   35° South -- Buenos Aires:
   
   
   San Francisco Bay Area, 37.5° North
   
   
   
6. Write the words SUNRISE and SUNSET as shown in the example. Note that the label positions and orientations are different for north vs. south latitudes.
   
   
7. Cut out the tool shape.
   
   
   
   
8. Glue or tape the tool shape to a piece of cardboard measuring 11.3 by 51.2 cm (4-1/2 by 20 inches). Glue stick works well for this.
   
   
   
   
   
   Your solar visualizer tool is now ready to use!
   
   Back to Using the Solar Visualizer Tool
   
   

Additional Notes

• The tool is designed to be held at arm's length, 57 cm (22 inches) from your face. If your reach is longer than this, hold the tool a little closer. If your reach is shorter, print out the tool at a proportionally smaller scale, such as 90% for a 20-inch reach.
  
  
• You can print out the tool at 50% scale to fit it on one sheet of paper. This is more convenient to carry around, but you need to hold it 29 cm (11 inches) from your face and keep it at that distance as you move the tool. Half-size (11-inch) analemma in Microsoft Word format
  
  
• Using a flat cardboard sheet is fine for practical purposes. However, for scientific accuracy, use a curved sheet of cardboard with an arch of 5 cm (2 inches) at the center. This keeps the whole tool a constant 57 cm from your face.
  
  
• On the Equator, the long central axis serves as both the SUNRISE and SUNSET horizon. You align the tool horizontally to the eastern horizon, move it straight up until it's directly above you, and then straight down to the western horizon.
  
  
• In the Southern Hemisphere, you move the tool through an arc that's tilted toward the north instead of the south. At noon, the tool points straight down (skinny end of the figure-8 down) toward the northern horizon.
  
  
• The marks on the two axes are spaced at intervals of 1 degree. On the short axis, the smaller tick marks are 1/4 degree apart, each representing 1 minute of solar motion in the direction of the red arrow.
  
  
• The little circles in the analemma are slightly smaller than the actual disk of the sun. The tool shows circles of actual solar disk size at the two solstices, at the ends of the analemma.
  
  
• The HelioTrak sundial and HelioTrak solar position visualizer are two different versions of the same tool. With the sundial, you are outside of the sky looking in, whereas with the position visualizer tool, you are inside of the sky looking out. That's why the analemmas of the two tools are mirror images of each other.
  
  
• The analemma printout is 100% accurate for the year 2022, but in other years, the dates are off by a partial day because of leap years and the annual quarter-day shift relative to the seasons. There are long-term shifts as well, so have your great-great grandchildren make updated tools.
  
  

Exact Solar Time Within Time Zone

The solar position visualizer tool accurately predicts the solar position for a given local solar time, such as 6:00 AM. Solar time is the same as the clock time if you are located at the reference meridian of your time zone.

For example, US Eastern Standard Time is based on the 75th west meridian. New York City is very close to this meridian, so clock time and solar time are nearly the same. But Detroit, in the same time zone, is located 8 degrees west of the meridian.


When sunrise occurs in New York City, the Sun is still below the horizon in Detroit, even though both cities use the same clock. To correct for this difference in Detroit, move the tool backward by 8 degrees or 8 cm (half the red arrow length), OR equivalently, subtract 32 minutes from Eastern Standard Time to get local Detroit solar time. 

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