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How to Determine Latitude From the Sun's Declination

The sun̵7;s declination is its angular distance from the celestial equator (the equator of the sphere of stars). The declination of the sun changes daily, moving north and south of the celestial equator. The sun is at its highest declination (23.5 degrees) on the summer solstice and at its lowest declination (-23.5 degrees) on the winter solstice. The sun is on the celestial equator with a declination of 0 degrees at the vernal and autumnal equinoxes. If you know the sun̵7;s declination and can measure its altitude at noon, you can find your latitude.

Things You'll Need

Table showing sun̵7;s declination
Protractor
String
Weight
Pen
Cardboard

Instructions

- 1
  Use a table to find the sun̵7;s declination on the day of your observation. Use positive degrees for declinations to the north of the celestial equator and negative degrees for declinations to the south.
- 2
  Prepare a measuring tool. Attach a weight to the bottom of a string and fix the top of the string to your cardboard sheet.
- 3
  Find the true horizon by measuring a 90-degree angle to your vertical string. Measure the degrees with your protractor and mark the horizontal line on the cardboard.
- 4
  Measure the altitude of the sun at noon. With your elbow touching your horizontal line, point at the sun with your arm. Measure the angle between the horizontal line and your arm with the protractor. This is the sun̵7;s altitude.
- 5
  Calculate your latitude using the following equation: latitude = declination + altitude ̵1; 90 degrees.

Astronomy