Right ascension is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the March equinox to the point in question above the Earth. When paired with declination, these astronomical coordinates specify the location of a point on the celestial sphere in the equatorial coordinate system.
A sextant is a doubly reflecting navigation instrument that measures the angular distance between two visible objects. The primary use of a sextant is to measure the angle between an astronomical object and the horizon for the purposes of celestial navigation.
Mīrzā Muhammad Tāraghay bin Shāhrukh, better known as Ulugh Beg, was a Timurid sultan, as well as an astronomer and mathematician.
Sidereal time is a system of timekeeping used especially by astronomers. Using sidereal time and the celestial coordinate system, it is easy to locate the positions of celestial objects in the night sky. Sidereal time is a "time scale that is based on Earth's rate of rotation measured relative to the fixed stars".
In astronomy and celestial navigation, the hour angle is the dihedral angle between the meridian plane and the hour circle.
Timeline of telescopes, observatories, and observing technology.
Uraniborg was an astronomical observatory and alchemy laboratory established and operated by the Danish astronomer Tycho Brahe. It was the first custom-built observatory in modern Europe, and the last to be built without a telescope as its primary instrument.
The backstaff is a navigational instrument that was used to measure the altitude of a celestial body, in particular the Sun or Moon. When observing the Sun, users kept the Sun to their back and observed the shadow cast by the upper vane on a horizon vane. It was invented by the English navigator John Davis, who described it in his book Seaman's Secrets in 1594.
Taqi ad-Din Muhammad ibn Ma'ruf ash-Shami al-Asadi was an Ottoman polymath active in Cairo and Istanbul. He was the author of more than ninety books on a wide variety of subjects, including astronomy, clocks, engineering, mathematics, mechanics, optics and natural philosophy.
The Constantinople observatory of Taqi ad-Din, founded in Constantinople by Taqi ad-Din Muhammad ibn Ma'ruf in 1577, was one of the largest astronomical observatories in the pre-modern world. However, it only existed for a few years and was destroyed in 1580.
Abu Mahmud Hamid ibn al-Khidr al-Khujandi was a Muslim Transoxanian astronomer and mathematician born in Khujand who lived in the late 10th century and helped build an observatory, near the city of Ray, in Iran.
The octant, also called a reflecting quadrant, is a reflecting instrument used in navigation.
The meridian circle is an instrument for timing of the passage of stars across the local meridian, an event known as a culmination, while at the same time measuring their angular distance from the nadir. These are special purpose telescopes mounted so as to allow pointing only in the meridian, the great circle through the north point of the horizon, the north celestial pole, the zenith, the south point of the horizon, the south celestial pole, and the nadir. Meridian telescopes rely on the rotation of the sky to bring objects into their field of view and are mounted on a fixed, horizontal, east–west axis.
In astronomy, sextants are devices depicting a sixth of a circle, used primarily for measuring the position of stars. There are two types of astronomical sextants, mural instruments and frame-based instruments.
A quadrant is an instrument used to measure angles up to 90°. Different versions of this instrument could be used to calculate various readings, such as longitude, latitude, and time of day. Its earliest recorded usage was in ancient India in Rigvedic times by Rishi Atri to observe a solar eclipse. It was then proposed by Ptolemy as a better kind of astrolabe. Several different variations of the instrument were later produced by medieval Muslim astronomers. Mural quadrants were important astronomical instruments in 18th-century European observatories, establishing a use for positional astronomy.
Reflecting instruments are those that use mirrors to enhance their ability to make measurements. In particular, the use of mirrors permits one to observe two objects simultaneously while measuring the angular distance between the objects. While reflecting instruments are used in many professions, they are primarily associated with celestial navigation as the need to solve navigation problems, in particular the problem of the longitude, was the primary motivation in their development.
Gotha Observatory was a German astronomical observatory located on Seeberg hill near Gotha, Thuringia, Germany. Initially the observatory was dedicated to astrometry, geodetic and meteorological observation and tracking the time.
The Ulugh Beg Observatory is an observatory in modern day Samarkand, Uzbekistan, which was built in the 1420s by the Timurid astronomer Ulugh Beg. This school of astronomy was constructed under the Timurid Empire, and was the last of its kind from the Islamic Medieval period. Islamic astronomers who worked at the observatory include Jamshid al-Kashi, Ali Qushji, and Ulugh Beg himself. The observatory was destroyed in 1449 and rediscovered in 1908.
Jonathan Sisson was a prominent English instrument maker, the inventor of the modern theodolite with a sighting telescope for surveying, and a leading maker of astronomical instruments.
