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AMATEUR ASTRONOMY FOR BEGINNERS: AN ONLINE GUIDE |
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POLAR ALIGNMENT OF GERMAN EQUATORIAL MOUNTS What is a German Equatorial Mount? Most small, store bought, equatorially mounted telescopes have what is called a German Equatorial Mount. This is a three axis mount, with two of the three axis forming a “T”. The telescope on one side of the “T” is balanced by a counterweight on the other side. The two axis that form the “T” are called the Right Ascension axis and Declination axis. These are in turn mounted on a third axis which allows the user to account for the latitude location of the telescope on the curvature of the earth.
Why do I need to polar align my equatorial mount? Because the earth’s surface is curved not everyone views the celestial pole from the same vantage point. Polar aligning your equatorial mount brings the telescope into alignment with earth’s rotational axis so that you can track a celestial object properly on a single axis, the right ascension axis, no matter where you are on the globe. |
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The Three Axis of a German Equatorial Mount.
LATITUDE AXIS - This axis allows you to account for your location in latitude on the curvature of the earth. Doing this adjusts the right ascension axis so that it is parallel to the earth’s rotational axis. The latitude axis also supports the entire telescope and the rest of the mount assembly on the tripod.
RIGHT ASCENSION AXIS - Once the telescope is properly aligned, this axis moves the scope in an east-west direction across the sky. This is also the tracking axis. It runs perpendicular to the declination axis and parallel to the earth’s rotational axis. It also supports the declination axle with its telescope and counterweight.
DECLINATION AXIS - Once the telescope is properly aligned, this axis moves the scope in a north-south direction across the sky. If you have a good alignment, once an object is found you will not need to move the telescope in declination until you change targets. This axis in turn runs perpendicular to the right ascension axis and perpendicular to the earth’s rotational axis. The declination axle also supports the counterweight and telescope at opposite ends. |
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LESSONS
Polar Alignment |