equatorial mounting

In astronomy, method of mounting a telescope to simplify the tracking of celestial objects. One axis (the polar axis) is mounted parallel to the rotation axis of the Earth so that the telescope can be turned about it to follow objects across the sky. The declination axis moves the telescope in declination and is clamped before tracking begins. Another advantage over the simpler altazimuth mounting is that the orientation of the image is fixed, permitting long-exposure photography.