Editing Epsilon Eridani (section)

=== Cataloguing ===
Epsilon Eridani has been known to astronomers since at least the 2nd century AD, when [[Claudius Ptolemy]] (a [[Greek astronomy|Greek astronomer]] from [[History of Alexandria|Alexandria]], [[Egypt (Roman province)|Egypt]]) included it in his catalogue of more than a thousand stars. The catalogue was published as part of his astronomical treatise the ''[[Almagest]]''. The constellation [[Eridanus (constellation)|Eridanus]] was named by Ptolemy – {{langnf|grc|Ποταμού|River}}, and Epsilon Eridani was listed as its thirteenth star. Ptolemy called Epsilon Eridani {{langnf|grc|ό τών δ προηγούμενος|a foregoing of the four}} (here {{lang|grc|δ}} is the number four). This refers to a group of four stars in Eridanus: [[Gamma Eridani|γ]], [[Pi Eridani|π]], [[Delta Eridani|δ]] and ε (10th–13th in Ptolemy's list). ε is the most western of these, and thus the first of the four in the apparent daily motion of the sky from east to west. Modern scholars of Ptolemy's catalogue designate its entry as ''"P 784"'' (in order of appearance) and ''"Eri 13"''. Ptolemy described the star's [[apparent magnitude|magnitude]] as 3.{{r|Baily1843|Verbunt2012}}

Epsilon Eridani was included in several star catalogues of [[Astronomy in medieval Islam|medieval Islamic]] astronomical treatises, which were based on Ptolemy's catalogue: in [[Abd al-Rahman al-Sufi|Al-Sufi]]'s ''[[Book of Fixed Stars]]'', published in 964, [[Abū Rayḥān al-Bīrūnī|Al-Biruni]]'s ''Mas'ud Canon'', published in 1030, and [[Ulugh Beg]]'s ''[[Zij-i Sultani]]'', published in 1437. Al-Sufi's estimate of Epsilon Eridani's magnitude was 3. Al-Biruni quotes magnitudes from Ptolemy and Al-Sufi (for Epsilon Eridani he quotes the value 4 for both Ptolemy's and Al-Sufi's magnitudes; original values of both these magnitudes are 3). Its number in order of appearance is 786.{{r|Al-Biruni1030}} Ulugh Beg carried out new measurements of Epsilon Eridani's coordinates in [[Ulugh Beg Observatory|his observatory]] at [[Samarkand]], and quotes magnitudes from Al-Sufi (3 for Epsilon Eridani). The modern designations of its entry in Ulugh Beg's catalogue are ''"U 781"'' and ''"Eri 13"'' (the latter is the same as Ptolemy's catalogue designation).{{r|Baily1843|Verbunt2012}}

In 1598 Epsilon Eridani was included in [[Tycho Brahe]]'s star catalogue, republished in 1627 by [[Johannes Kepler]] as part of his ''[[Rudolphine Tables]]''. This catalogue was based on Tycho Brahe's observations of 1577–1597, including those on the island of [[Hven]] at his observatories of [[Uraniborg]] and [[Stjerneborg]]. The sequence number of Epsilon Eridani in the constellation Eridanus was 10, and it was designated {{Langnf|la|Quae omnes quatuor antecedit|which precedes all four}}; the meaning is the same as Ptolemy's description. Brahe assigned it magnitude 3.{{r|Baily1843|Verbunt2010a}}

Epsilon Eridani's [[Bayer designation]] was established in 1603 as part of the ''[[Uranometria]]'', a star catalogue produced by German celestial cartographer [[Johann Bayer]]. His catalogue assigned letters from the [[Greek alphabet]] to groups of stars belonging to the same visual magnitude class in each constellation, beginning with alpha (α) for a star in the brightest class. Bayer made no attempt to arrange stars by relative brightness within each class. Thus, although Epsilon is the fifth letter in the Greek alphabet,<ref name=jha17_50_189 /> the star is the [[List of stars in Eridanus|tenth-brightest in Eridanus]].<ref name=ybsc1991 /> In addition to the letter ε, Bayer had given it the number 13 (the same as Ptolemy's catalogue number, as were many of Bayer's numbers) and described it as {{lang-for|la|Decima septima|the seventeenth}}.{{#tag:ref|This is because Bayer designated 21 stars in the northern part of Eridanus by preceding along the 'river' from east to west, starting from β ({{lang|la|Supra pedem Orionis in flumine, prima}}, meaning ''above [[Rigel|the foot]] of [[Orion (constellation)|Orion]] in the river, the first'') to the twenty-first, σ ({{lang|la|Vigesima prima}}, that is ''the twenty-first''). Epsilon Eridani was the seventeenth in this sequence. These 21 stars are: β, λ, ψ, b, ω, μ, c, ν, ξ, ο (two stars), d, A, γ, π, δ, ε, ζ, ρ, η, σ.<ref name="Bayer1603" />|group=note|name=bayer}} Bayer assigned Epsilon Eridani magnitude 3.{{r|Bayer1603}}

In 1690 Epsilon Eridani was included in the star catalogue of [[Johannes Hevelius]]. Its sequence number in constellation Eridanus was 14, its designation was {{langnf|la|Tertia|the third}}, and it was assigned magnitude 3 or 4 (sources differ).{{r|Baily1843|Verbunt2010b}} The star catalogue of English astronomer [[John Flamsteed]], published in 1712, gave Epsilon Eridani the [[Flamsteed designation]] of 18&nbsp;Eridani, because it was the eighteenth catalogued star in the constellation of Eridanus by order of increasing [[right ascension]].<ref name=SIMBAD /> In 1818 Epsilon Eridani was included in [[Friedrich Bessel]]'s catalogue, based on [[James Bradley]]'s observations from 1750–1762, and at magnitude 4.{{r|Bessel1818}} It also appeared in [[Nicolas Louis de Lacaille]]'s catalogue of 398 principal stars, whose 307-star version was published in 1755 in the {{lang|fr|Ephémérides des Mouvemens Célestes, pour dix années, 1755–1765}},{{r|Lacaille1755}} and whose full version was published in 1757 in {{lang|la|Astronomiæ Fundamenta}}, Paris.{{r|Lacaille1757}} In its 1831 edition by [[Francis Baily]], Epsilon Eridani has the number 50.{{r|Baily1831}} Lacaille assigned it magnitude 3.{{r|Lacaille1755|Lacaille1757|Baily1831}}

In 1801 Epsilon Eridani was included in {{lang|fr|[[Histoire céleste française]]}}, [[Joseph Jérôme Lefrançois de Lalande]]'s catalogue of about 50,000 stars, based on his observations of 1791–1800, in which observations are arranged in time order. It contains three observations of Epsilon Eridani.<ref name=lalande group=note>1796 September 17 (page 246), 1796 December 3 (page 248) and 1797 November 13 (page 307)</ref>{{r|Lalande1801}} In 1847, a new edition of Lalande's catalogue was published by Francis Baily, containing the majority of its observations, in which the stars were numbered in order of [[right ascension]]. Because every observation of each star was numbered and Epsilon Eridani was observed three times, it got three numbers: 6581, 6582 and 6583.{{r|Baily1847}} (Today numbers from this catalogue are used with the prefix "Lalande", or "Lal".{{r|Lal}}) Lalande assigned Epsilon Eridani magnitude 3.{{r|Lalande1801|Baily1847}} Also in 1801 it was included in the catalogue of [[Johann Bode]], in which about 17,000 stars were grouped into 102 constellations and numbered (Epsilon Eridani got the number 159 in the constellation Eridanus). Bode's catalogue was based on observations of various astronomers, including Bode himself, but mostly on Lalande's and Lacaille's (for the southern sky). Bode assigned Epsilon Eridani magnitude 3.{{r|Bode1801}} In 1814 [[Giuseppe Piazzi]] published the second edition of his star catalogue (its first edition was published in 1803), based on observations during 1792–1813, in which more than 7000 stars were grouped into 24 hours (0–23). Epsilon Eridani is number 89 in hour 3. Piazzi assigned it magnitude 4.{{r|Piazzi1814}} In 1918 Epsilon Eridani appeared in the [[Henry Draper Catalogue]] with the designation HD&nbsp;22049 and a preliminary spectral classification of K0.<ref name=ahco91_1 />