In the field of astronomy, the angle to an astronomical object above the horizon is called altitude; instead of elevation. Consequently, an EL/AZ mount is often called an ALT/AZ or altazimuth mount.
However, some astronomical telescopes can be moved in altitude only; azimuth is fixed. Called meridian telescopes, these telescopes are restricted to viewing only those astronomical objects which happen to lie in the same meridian as the telescope. Of course, the earth's rotation brings every visible astronomical object into the telescopes's field of view many times during the course of a year. A further explanation, provided by Universita' Degli Studi di Bologna Dipartimento di Astronomia, is available here.
• Meridian Optical Telescope: 6-inch Meridian Circle Telescope