### Use your fingers to measure the altitude of stars in the sky for degree elevation above the horizon.

**SCIENCE** – The celestial dome is an imaginary dome with the Earth at its center, serving as the location for other celestial objects. Altitude (height) of celestial objects is measured in degrees, starting from 0° at the horizon to 90° at the zenith (the point directly above us). In this experiment, you will measure the estimated altitude of a star using your fingers as a measuring tool. You will also use the angle of an object’s shadow to determine the altitude of the Sun.

**Learning Objective**

This experiment aims to measure the estimated altitude of a star using your fingers and closed fist.

**Materials**

Hand

**Procedure**

- On a clear night, stand in an open space and choose a brightly shining star.
- Use both hands and the methods depicted in Figures 3.1 and 3.2 to measure the altitude of the star above the horizon. For example, if you measure a star three closed fists and three fingers above the horizon, the altitude of the star would be approximately 35° above the horizon.

**Results**

The altitude of stars varies. In the given example, the altitude is 35°.

**Why?**

A coordinate system called the altazimuth system is used in astronomy to determine the positions of celestial objects based on altitude (angular height above the horizon) and azimuth (angular distance around the horizon). (See further explanations about azimuth in the horizontal dimension.) In explaining this coordinate system, it is accurate to envision the celestial dome (an imaginary dome with the Earth at its center and other celestial objects surrounding it). The coordinates (two numbers representing a location) altitude and azimuth are angles used to determine the position of an object on the celestial dome.

In this experiment, we need to find its altitude coordinates. Altitude is the vertical measurement on the celestial dome, measured in degrees above the horizon, ranging from 0° at the horizon to 90° at the zenith. The width of your hand parts can be used to estimate the altitude of celestial objects.

**Try a New Approach**

Altitude representing the angular distance above the horizon can be imagined as parallel circles of celestial objects, decreasing from the horizon to the zenith. What is the comparison between altitude and latitude (lines of latitude)? Latitude represents imaginary parallel circles representing the north and south angular distance of celestial objects or the equator (an imaginary line running from east to west, encircling the middle part of a celestial object or the celestial dome). On a clear night, face north and locate the seven stars of the Big Dipper (see the following figure).

Follow two stars in the dipper’s bowl until you reach Polaris above the horizon. Use your hand to measure the estimated altitude of Polaris above the horizon. Compare the altitude of Polaris with your location’s latitude on a map. Repeat this measurement with different latitudes or ask a friend in another city to perform the same measurement. For more information on the comparison between altitude and latitude of celestial objects, you can read the book titled “Constellations for Every Kid” by Janice VanCleave (New York: Wiley, 1997), pages 64-72.