What is an astrolabe?
The astrolabe is a very ancient astronomical computer for solving problems relating to time and the position of the Sun and stars in the sky. Several types of astrolabes have been made. By far the most popular type is the planispheric astrolabe, on which the celestial sphere is projected onto the plane of the equator. A typical old astrolabe was made of brass and was about 6 inches (15 cm) in diameter, although much larger and smaller ones were made. Astrolabes are used to show how the sky looks at a specific place at a given time. This is done by drawing the sky on the face of the astrolabe and marking it so positions in the sky are easy to find. To use an astrolabe, you adjust the moveable components to a specific date and time. Once set, the entire sky, both visible and invisible, is represented on the face of the instrument. This allows a great many astronomical problems to be solved in a very visual way. Typical uses of the astrolabe include finding the time during the day or nigh
An astrolabe is an ancient instrument used to measure the position of the sun or stars. In the past, it was useful for a number of purposes such as determining the time of day or night and measuring one’s current position in relation to the north and south poles. More specifically, a mariner’s astrolabe was used to determine the latitude of a ship at sea and guide its direction. In the 15th and 16th centuries, for example, navigators used the mariner’s astrolabe to identify their position at sea, sail to a certain latitude then sail east or west along that latitude until they reached their destination (Morrison, 2009). Similar to the mariner’s astrolabe, the Asia-Pacific ESD Astrolabe aims to assist UNESCO Member States in determining the current position of ESD in their country and guiding ESD in a specified direction. To determine the position of ESD in the national context, the Astrolabe assists countries in taking stock of ESD linkages in national policy, mapping current ESD-relate
The astrolabe is an ancient scientific instrument dating back to 170 B.C. Complex planetary astrolabes were used to measure the altitude of celestial bodies and to track their movements. From these calculations, latitude and time could also be determined. In the sixteenth century a simpler nautical or mariner’s astrolabe was developed for navigational use. The simple astrolabe consists of an outer disk with the circumference marked off in degrees. At the centre of the disk is a movable pointer called the alidade. To use, the navigator aligned the horizontal axis of the astrolabe with the horizon. He then pointed the alidade at the sun or polar star and read its position on the outer disk. This measured the angle of inclination of the sun or star from the earth’s horizon. By consulting an ephemeris or astronomical tables with this reading, the navigator could fix his latitude.