Editing Astronomical naming conventions (section)

=== Catalogues ===
{{main|Star catalogue}}

With the advent of the increased light-gathering abilities of the telescope, many more stars became visible, far too many to all be given names. Instead, they have [[Stellar designation|designations]] assigned to them by a variety of different [[star catalogue]]s. Older catalogues either assigned an arbitrary number to each object, or used a simple systematic naming scheme based on the constellation the star lies in, like the older [[Ptolemy]]'s Almagest in Greek from [[AD 150|150]] and [[Abd al-Rahman al-Sufi|Al-Sufi]]'s [[Book of Fixed Stars]] in Arabic from 964. The variety of sky catalogues in use means that most bright stars have multiple designations.

In 1540, the Italian astronomer [[Alessandro Piccolomini|Piccolomini]] released the book ''De le Stelle Fisse'' (On the Fixed Stars) which include star maps of 47 constellations where he numbered the stars in magnitude order using latin letters.<ref name="ridpath">{{cite web |last=Ridpath |first=Ian |title=Alessandro Piccolomini's star atlas |url=http://www.ianridpath.com/startales/piccolomini.html}}</ref> 

==== Bayer designation ====
{{main|Bayer designation|Table of stars with Bayer designations}}

The [[Bayer designation]]s of about 1,500 brightest stars were first published in 1603. In this list, a star is identified by a lower-case [[Greek alphabet#Letters|letter of the Greek alphabet]], followed by the Latin name of its parent constellation. The Bayer designation uses the possessive form of a constellation's name, which in almost every case ends in ''is'', ''i'' or ''ae''; ''um'' if the constellation's name is plural ''(see [[88 modern constellations#Modern constellations|genitive case for constellations]])''. In addition, a three-letter abbreviation is often used . Examples include [[Alpha&nbsp;Andromedae]] (''α And'') in the constellation of Andromeda, [[Alpha&nbsp;Centauri]] (''α Cen''), in the constellation Centaurus, [[Alpha&nbsp;Crucis]] (''α Cru'') and [[Beta&nbsp;Crucis]] (''β Cru''), the two brightest stars in the constellation Crux, the Southern Cross, [[Epsilon&nbsp;Carinae]] (''ε Car'') in Carina, [[Lambda&nbsp;Scorpii]] (''λ Sco'') in Scorpius  and [[Sigma&nbsp;Sagittarii]] (''σ Sgr'') in Sagittarius. After all twenty-four Greek letters have been assigned, upper and lower case Latin letters are used, such as for [[A&nbsp;Centauri]] (''A Cen''), [[D&nbsp;Centauri]] (''D Cen''), [[G&nbsp;Scorpii]] (''G Sco''), [[P Cygni]] (''P Cyg''), [[b&nbsp;Sagittarii]] (''b Sgr''), [[HD 117440|d&nbsp;Centauri]] (''d Cen'') and [[HD 90853|s&nbsp;Carinae]] (''s Car'').

As the resolving power of telescopes increased, numerous objects that were thought to be a single object were found to be optical [[star system]]s that were too closely spaced in the sky to be discriminated by the human eye. This led to a third iteration, where numeric superscripts were added to distinguish those previously unresolved stars. Examples include [[Theta Sagittarii]] (''θ Sgr'') later distinguished as Theta¹ Sagittarii (''θ¹ Sgr'') and Theta² Sagittarii (''θ² Sgr''), each being their own (physical) star system with two and three stars, respectively.

==== Flamsteed designation ====
{{Further|List of constellations using Flamsteed star designations}}

[[Flamsteed designation]]s consist of a number and the Latin genitive of the constellation the star lies in. Examples include [[51 Pegasi]] and [[61 Cygni]]. About 2,500 stars are catalogued. They are commonly used when no Bayer designation exists, or when the Bayer designation uses numeric superscripts such as in [[Rho1 Cancri|Rho¹&nbsp;Cancri]]. In this case, the simpler Flamsteed designation, [[55 Cancri]], is often preferred.

==== Modern catalogues ====
Most modern catalogues are generated by computers, using high-resolution, high-sensitivity telescopes, and as a result describe very large numbers of objects. For example, the [[Guide Star Catalog II]] has entries on over 998&nbsp;million distinct astronomical objects. Objects in these catalogs are typically located with very high resolution, and assign designations to these objects based on their position in the sky. An example of such a designation is ''SDSSp J153259.96&minus;003944.1'', where the initialism ''SDSSp'' indicates that the designation is from the "[[Sloan Digital Sky Survey]] preliminary objects", and the other characters indicate [[celestial coordinates]] ([[astronomical epoch|epoch]] 'J', [[right ascension]] 15{{sup|h}}32{{sup|m}}59.96{{sup|s}}, [[declination]] &minus;00°39′44.1″).