In the 1980s, charge-coupled devices (CCDs) replaced photographic plates and reduced optical uncertainties to one milliarcsecond. Started in the late 19th century, the project Carte du Ciel to improve star mapping couldn't be finished but made photography a common technique for astrometry. Automated plate-measuring machines and more sophisticated computer technology of the 1960s allowed more efficient compilation of star catalogues. Astrographs using astronomical photographic plates sped the process in the early 20th century. He made the first measurement of stellar parallax: 0.3 arcsec for the binary star 61 Cygni.īeing very difficult to measure, only about 60 stellar parallaxes had been obtained by the end of the 19th century, mostly by use of the filar micrometer. His cataloguing of 3222 stars was refined in 1807 by Friedrich Bessel, the father of modern astrometry. The stellar movement proved too insignificant for his telescope, but he instead discovered the aberration of light and the nutation of the Earth's axis. James Bradley first tried to measure stellar parallaxes in 1729. When telescopes became commonplace, setting circles sped measurements Taqi al-Din measured the right ascension of the stars at the Constantinople Observatory of Taqi ad-Din using the 'observational clock' he invented. In the 16th century, Tycho Brahe used improved instruments, including large mural instruments, to measure star positions more accurately than previously, with a precision of 15–35 arcsec. Like the earlier catalogs of Hipparchus and Ptolemy, Ulugh Beg's catalogue is estimated to have been precise to within approximately 20 minutes of arc. In the 15th century, the Timurid astronomer Ulugh Beg compiled the Zij-i-Sultani, in which he catalogued 1,019 stars. His observations on eclipses were still used centuries later in Simon Newcomb's investigations on the motion of the Moon, while his other observations of the motions of the planets Jupiter and Saturn inspired Laplace's Obliquity of the Ecliptic and Inequalities of Jupiter and Saturn. Ibn Yunus observed more than 10,000 entries for the Sun's position for many years using a large astrolabe with a diameter of nearly 1.4 metres.

In the 10th century, Abd al-Rahman al-Sufi carried out observations on the stars and described their positions, magnitudes and star color furthermore, he provided drawings for each constellation, which are depicted in his Book of Fixed Stars. Hipparchus's successor, Ptolemy, included a catalogue of 1,022 stars in his work the Almagest, giving their location, coordinates, and brightness. Hipparchus compiled a catalogue with at least 850 stars and their positions.

In doing so, he also developed the brightness scale still in use today. This can be dated back to Hipparchus, who around 190 BC used the catalogue of his predecessors Timocharis and Aristillus to discover Earth's precession. The history of astrometry is linked to the history of star catalogues, which gave astronomers reference points for objects in the sky so they could track their movements.

Concept art for the TAU spacecraft, a 1980s era study which would have used an interstellar precursor probe to expand the baseline for calculating stellar parallax in support of Astrometry

Astrometry vs. doppler method