With more advanced equipment, but still cheap in comparison to professional setups, amateur astronomers can measure the light spectrum emitted from astronomical objects, which can yield high-quality scientific data if the measurements are performed with due care.

But in the later nineteenth and early twentieth centuries, with increasing precision of astronomical measurements, it began to be suspected, and was eventually established, that the rotation of the Earth ( i. e. the length of the day ) showed irregularities on short time scales, and was slowing down on longer time scales.

A number of experimenters initially claimed to have identified the effect using astronomical measurements, and the effect was eventually considered to have been finally identified in the spectral lines of the star Sirius B by W. S.

Calibration of the astronomical distance scale relies on a sequence of indirect and sometimes uncertain measurements relating the closest objects, for which distances can be directly measured, to increasingly distant objects.

The second thus defined is consistent with the ephemeris second, which was based on astronomical measurements.

Tycho Brahe was granted an estate on the island of Hven and the funding to build the Uraniborg, an early research institute, where he built large astronomical instruments and took many careful measurements, and later Stjerneborg, underground, when he discovered that his instruments in the former were not sufficiently steady.

Precise astronomical angular measurements require knowledge of the Earth's rotation rate and nutation, both of which are influenced by Earth tides.

However, using an astronomical interferometer, measurements of the radius of the star can be made directly to an accuracy of 0. 5 %.

* Anomalous increase of the astronomical unit: Recent measurements indicate that planetary orbits are widening faster than if this were solely through the sun losing mass by radiating energy.

Composed of three books, it deals with the geometry of the sphere and its application in astronomical measurements and calculations.

It was a very large mural sextant that achieved a high level of accuracy for astronomical measurements.

Where metres per second are several orders of magnitude too slow to be convenient, such as in astronomical measurements, velocities may be given in kilometres per second, where 1 km / s is 1000 metres per second.

By comparing astronomical observations with laboratory measurements, astrochemists can infer the elemental abundances, chemical composition, and temperatures of stars and interstellar clouds.

This formula was important for enabling more accurate photographic measurements of the intensities of faint astronomical sources.

The calibration program includes measurements that are made relative to on-board calibration sources or to assess internal detector noise levels as well as observations of astronomical standard stars and fields, needed to determine absolute flux conversions and astrometric transformations.

Due to the necessity of recent astronomical measurements, the date of the holiday is not officially declared until February of the previous year.

The date of the holiday is not officially declared until February of the previous year, due to the need for recent astronomical measurements.

But in the later nineteenth and early 20th centuries, with the increasing precision of astronomical measurements, it began to be suspected, and was eventually established, that the rotation of the Earth ( i. e. the length of the day ) showed irregularities on short time scales, and was slowing down on longer time scales.

In 1946 Ryle and Vonberg were the first people to publish interferometric astronomical measurements at radio wavelengths, although it is claimed that Joseph Pawsey from the University of Sydney had actually made interferometric measurements earlier in the same year.

Adrain, Gauss, and Legendre all motivated the method of least squares by the problem of reconciling disparate physical measurements ; in the case of Gauss and Legendre, the measurements in question were astronomical, and in Adrain's case they were survey measurements.

Scientists can obtain sensitive photometric measurements of astronomical targets.

In order to test these predictions, it is necessary to reconstruct the primordial abundances as faithfully as possible, for instance by observing astronomical objects in which very little stellar nucleosynthesis has taken place ( such as certain dwarf galaxies ) or by observing objects that are very far away, and thus can be seen in a very early stage of their evolution ( such as distant quasars ).

* 2005 – The Mars Exploration Rovers perform the first astronomical observations ever taken from the surface of another planet, imaging an eclipse by Mars's moon Phobos.

The first photograph of an astronomical object ( the Moon ) was taken in 1840, but it was not until the late 19th century that advances in technology allowed for detailed stellar photography.

Many famous astronomical surveys were taken using photographic plates, including the first Palomar Observatory Sky Survey ( POSS ) of the 1950s, the follow-up POSS-II survey of the 1990s, and the UK Schmidt survey of southern declinations.

Eight individual frames taken from a video of the lunar crater Clavius showing the effect of the Earth's atmosphere on astronomical images

In the course of the expedition-to quote the words of Sir Roderick Murchison addressed to the youthful traveller when, in 1870, he was presented with the Victoria Medal of the Royal Geographical Society of London-" from Kratie in Cambodia to Shanghai 5392 miles were traversed, and of these, 3625 miles, chiefly of country unknown to European geography, were surveyed with care, and the positions fixed by astronomical observations, nearly the whole of the observations being taken by Garnier himself ".

Mathematical models can give an accurate model of the effects of astronomical seeing on images taken through ground-based telescopes.

In the body of the work, we hear that he had been at Paris and Constantinople ; had served the Sultan of Egypt a long time in his wars against the Bedouin, had been vainly offered by him a princely marriage and a great estate on condition of renouncing Christianity, and had left Egypt under Sultan Melech Madabron ( al-Muzaffar Sayf-ad-Din Hajji I who reigned in 1346-1347 ); had been at Mount Sinai, and had visited the Holy Land with letters under the great seal of the sultan, which gave him extraordinary facilities ; had been in Russia, Livonia, Kraków, Lithuania, " en roialme daresten " ( Dristra or Silistra in Bulgaria ), and many other parts near Tartary, but not in Tartary itself ; had drunk of the Well of Youth at Polombe ( Quilon on the Malabar coast ), and still seemed to feel the better ; had taken astronomical observations on the way to Lamory ( Sumatra ), as well as in Brabant, Germany, Bohemia and still farther north ; had been at an isle called Pathen in the Indian Ocean ; had been at Cansay ( Hangchow-fu ) in China, and had served the emperor of China fifteen months against the king of Mann ; had been among rocks of adamant in the Indian Ocean ; had been through a haunted valley, which he places near " Milstorak " ( i. e. Malasgird in Armenia ); had been driven home against his will in 1357 by arthritic gout ; and had written his book as a consolation for his " wretched rest ".

In the USA and some other regions in the Northern Hemisphere, the astronomical March equinox ( currently around 21 March ) is often taken to mark the first day of spring, and the Northern solstice is sometimes taken as the first day of summer ( usually 21 June in the Northern Hemisphere ).

Local topography, bay and river orientation, depth of the sea bottom, astronomical tides, as well as other physical features are taken into account, in a predefined grid referred to as a SLOSH basin.

The location of an Alderson point is dictated by the balance of the fundamental forces, which for a Sol-like star leads to points that can be several astronomical units apart by direct line – even farther when orbital paths are taken into account.

Literature searches that previously would have taken days or weeks can now be carried out in seconds via the ADS search engine, custom-built for astronomical needs.

ADS has allowed literature searches that would previously have taken days or weeks to carry out to be completed in seconds, and it is estimated that ADS has increased the readership and use of the astronomical literature by a factor of about three since its inception.

It occurs on the first Sunday after the first full moon on or after 21 March, a date taken, in accordance with an ancient ecclesiastical tradition, to be that of the spring equinox, but which does not always correspond to the astronomical equinox.

HCO houses a collection of approximately 500, 000 astronomical plates taken between the mid-1880s and 1989 ( with a gap from 1953 – 68 ).

* The painting has been compared to an astronomical photograph of a star named V838 Monocerotis, taken by the Hubble in 2004.

The term alignment is sometimes taken to imply that the rows were placed purposely in relation to other factors such as other monuments or topographical or astronomical features.

The following passage which reports an astronomical sighting is taken from an account compiled by Jacobus Malvecius in the 15th century:

Furthermore, Su Song must have taken advantage of the astronomical findings of his political rival and contemporary astronomer Shen Kuo.

Based on Lescarbault ’ s " transit ", Le Verrier computed Vulcan ’ s orbit: it supposedly revolved about the Sun in a nearly circular orbit at a distance of 21 million kilometres, or 0. 14 astronomical units.

* First contact, the moment in astronomical transit when the apparent positions of the two bodies first touch

Before the American Revolutionary War, on 3 June 1769, Hopkins was involved in the observation of a rare astronomical event, the transit of Venus across the face of the sun.

The term transit or astronomical transit has three meanings in astronomy:

* A transit is the astronomical event that occurs when one celestial body appears to move across the face of another celestial body, hiding a small part of it, as seen by an observer at some particular vantage point.

* December 9-A transit of Venus across the Sun is observed in Muddapur, India, by an astronomical expedition led by Pietro Tacchini.

He unsuccessfully attempted to observe the transit of Venus just one month later, but due to inaccurate astronomical tables he did not realize that it was not visible from most of Europe, including Paris.

Deimos astronomical transit | transits the Sun, as seen by Mars Rover MER-B | Opportunity on March 4, 2004

Phobos astronomical transit | transits the Sun, as seen by Mars Rover MER-B | Opportunity on March 10, 2004

In 1761, John Winthrop, the Hollis Professor of Mathematics and Natural Philosophy, arranged the first American astronomical expedition to observe Venus's transit over the Sun.

Ford's astronomical adventures in Europe were brought to a conclusion when he visited Greenwich Observatory and stood, on 31 May, " right below the transit slit, with one foot at 23h 59m 59. 999s and the other one at 00h 00m 00. 001s.

The firm produced hundreds of astronomical instruments such as mural circles, transit circles, sextants, and other astronomical instruments for observatories around the world.

In September 1874 a French astronomical mission conveyed by the sailing ship La Dive spent just over three months on Saint-Paul to observe the transit of Venus ; geologist Charles Vélain took the opportunity to make a significant geological survey of the island.

He often traveled to London where he ordered astronomical equipment from Jesse Ramsden and John Dollond: a 4-foot transit telescope in 1765, 3. 5-foot achromatic telescope in 1770, 8-foot mural quadrant in 1777, and meridian circle in 1788.

A year earlier, the Paris Observatory had sent astronomical instruments to the city of Bragado, Buenos Aires, to observe a transit of Venus in front of the Sun, for which the location was particularly suitable, and which raised considerable interest in scientific circles.