The angle between an object and the horizon, from 0° (on the horizon) to 90° (at the zenith); also called elevation. Objects are usually well placed above 30°. With azimuth it locates an object in your local sky.
ToolsWhat to see tonight?, Celestial fix, Interactive atlas
Related terms
- Azimuth
An object’s direction along the horizon, measured from north towards east: 0° north, 90° east, 180° south, 270° west. With altitude it tells you where to look. Some older books count it from the south: check the convention.
- Zenith
The point in the sky directly overhead, at 90° altitude. That is where you look through the least air, so images are at their sharpest and brightest. Its opposite, below your feet, is the nadir.
- Horizon
The circle where the sky seems to meet the ground, at 0° altitude. The astronomical horizon is a perfect plane; the real one is hidden by trees, hills and buildings. Near the horizon, thick air and light pollution degrade the view.
- Alt-azimuth mount
A mount with two axes, one vertical (azimuth) and one horizontal (altitude), like a photo tripod. Intuitive and with no polar alignment, it needs both axes moved to follow an object. In long-exposure imaging the field rotates as the minutes pass.
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