Height (astronomy)

Height of a star.

In astronomy is called a height (a) of a star to the arc of vertical counted from the horizon to the star. Its absolute value is always less than or equal to 90 ° and, by agreement, it is a positive value if the star is visible (ie if it is on the horizon) and negative if it is not visible (ie if it is under the horizon). It is one of the two horizontal coordinates, the other being the azimuth or azimuth. The height and the azimuth are coordinates that depend on the position of the observer. That is to say a same star in a same moment are seen under different horizontal coordinates by different observers located in different points of the Earth. This means that these coordinates are local. At present to measure the height of a star uses an instrument called sextant. If the height of the sun is measured, care must be taken not to damage the eyes. The horizontal coordinates can be calculated mathematically. This information at the same time can be used to calculate the solar radiation received by the earth in a certain period of time or the projection of shadows of an element that does not yet exist as a building, among many other functions.

On-line solar almanac - allows you to calculate the horizontal coordinates for any place in the world at a specific date and time

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