Glossary | Telescopes | Mount | Altitude
Altazimuth mounts have two axes. One axis can be used to adjust the optic’s altitude, the other changes the viewing direction (azimuth). Under the heading altitude, the technical data indicates through how many degrees the altitude axis can be moved.
Since altazimuth mounts can also be used with optics for terrestrial observation, a negative value for the smallest angle can be useful. A negative value allows a view down into a valley.