Measuring Altitude / Height of the Sun

The height of the sun above the true horizon is often called its ALTITUDE. (Sometimes called elevation.) This is not the altitude or elevation referring to height above sea level. The sun's altitude is measured from the horizon on level ground or the sea at "0" degrees. Straight over head is "90" degrees. (Some sun position programs measure straight up as "0")

Altitude is best measured with a clinometer or Abney Level. Clinometers built into mirror sighting compasses are not very accurate. The clinometer on the Suunto Tandem is very good, but expensive. If you can find the materials, you can make a very accurate one for a few dollars. (See Homemade Clinometer)

Abney Level

Suunto Tandum

Small Homemade

NEVER look directly at a bright sun. You can use the shadow of the sun to measure its altitude. If you point a clinometer at the sun, NOT looking at the sun, watch where the shadow and reflection of the sun merge along a straight edge of the clinometer. You can practice indoors with a distant bright light.

You CAN look at the sun through welding filters available from welding equipment suppliers. You need the maximum darkness #14. You can look through a clinometer or Abney Level with these filters. Make sure the filter is between your eyes and the sun. Very carefully open your eyes to make sure the filter covers both eyes. To be extra safe attach the filter as a window to a larger piece of material to prevent burning your precious eyes. The round welding filters DO NOT come dark enough only he rectangular ones. Cost: about $2.00. I don't think the auto darkening filters are safe. Astronomy neutral density filters have a different scale of density starting with low numbers the darkest. If you use dark neutral density filters in an optical system near the plane of focus they can get very hot and break doing damage to eyes and equipment. BE CAREFUL!

Measuring Sun Elevation with
Abney Level and Welders Filter

With Suunto Tandum and Filter

If the sun is low, not very bright or not visible, you can look directly through your clinometer to see where the sun is or should be.

If you have a computer sun program or print out from the Internet, the sun's altitude is a very good compass and clock. During the middle of the day it is not as accurate, but early and late it is very accurate and can be helpful in determining true north, where the sun rose and where it will set.

It is not easy to judge a true horizon by eye. If you are on a high point, things that are closer appear higher than things in the distance such as the horizon at the ocean.

A beach may appear to go up hill if there is a ridge at the water's edge, but it can actually be level or even slightly down hill. A clinometer is useful to judge these slopes.

The ocean horizon does drop below the true horizon "0" degrees because of the curvature of the earth. The higher you are above sea level the more the ocean horizon "dips".

Make or buy a clinometer to learn measuring the altitude of objects.

© Copyright 1999-2004 Ron Dexter. All Rights Reserved.