Glossary term: Acimut
Description: En un sistema de coordenadas horizontales, el acimut se refiere a la dirección (ángulo a lo largo del horizonte) en la que se encuentra el objeto. Se mide en grados a partir del norte y hacia el este. Los valores del acimut cubren un círculo completo de 0 a 360 grados. En otras palabras, si dibujas un arco imaginario en la esfera celeste desde el objeto hasta el horizonte y perpendicular al horizonte, el acimut te indicará la ubicación del punto en el que este arco se encuentra con el horizonte. Un objeto situado directamente al norte tendría 0 grados de acimut, un objeto situado directamente al este tendría 90 grados de acimut y así sucesivamente. En los libros de texto más antiguos utilizados en varios países, la convención era empezar a medir el acimut desde el sur hacia el oeste. Por lo tanto, los valores de acimut en esos libros de texto se desplazarían 180 grados.
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Term and definition status: The original definition of this term in English have been approved by a research astronomer and a teacher The translation of this term and its definition is still awaiting approval
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Related Diagrams
Horizontal Coordinate System
Caption: This image shows the horizontal coordinate system of an observer on Earth. On the right we see the coordinate system in the local context of the observer. The observer appears here as a point surrounded by the celestial sphere. The ground appears as a plane, while the Earth is round, we can approximate the ground in the area around the observer as a plane. The line where this plane intersects with the celestial sphere is the horizon. The point directly above the observer is the zenith, the point directly below the observer is the nadir which is hidden by the ground.
Two coordinates define this coordinate system, altitude and azimuth, hence the reason this sometimes called an alt-az coordinate system. The altitude is zero at the horizon, maximum (90°) at the zenith and minimum (-90°) at the nadir. Azimuth is the angle around the horizon. Most commonly this is defined to be zero in the direction of north. Any point on the celestial sphere can be defined by these two coordinates. However what objects appear on these position will depend on the time and the location of the observer.
On the left-hand part of the diagram, we can see that when we put the observer and their local horizontal coordinate system in a global context, that the parts of the sky the observer can see depend on their position on the Earth and on the rotation of the Earth. The zenith points perpendicular to the Earth's surface so the position on the sky the zenith and nadir correspond to is dependent on the observer's latitude. The horizon also depends on the observer's position on the Earth.
Credit: Maria Cristina Fortuna/IAU OAE
License: CC-BY-4.0 Creative Commons Reconocimiento 4.0 Internacional (CC BY 4.0) icons
