Two mounts in one
Although at first glance the AZ-EQ Avant mount looks like a conventional altazimuth mount, it can actually be used in two modes.
In altazimuth (AZ) mode, the mount moves horizontally in a 360° circle (azimuth) and vertically (altitude) from the horizon to the zenith, the point in the sky immediately above the observer. This makes it simple to locate astronomical targets. But to follow these objects as they move across the night sky in an arc it’s necessary to make adjustments in both altitude and azimuth axes.
In equatorial (EQ) mode, the whole mount head is tilted on an adjustable wedge so that it points to the North Celestial Pole (in the northern hemisphere) or South Celestial Pole (in the southern hemisphere), around which the sky appears to rotate. This means that once you’ve aligned the telescope on an object using the ‘horizontal’ adjustment (right ascension – RA) and the ‘vertical’ adjustment (declination – Dec.), it’s only necessary to make adjustments in the RA plane to follow the object as it traverses the sky.