Bayer designation

Bayer assigned a lowercase Greek letter (alpha (α), beta (β), gamma (γ), etc.)

[3] Bayer did not label "permanent" stars with uppercase letters (except for A, which he used instead of a to avoid confusion with α).

However, a number of stars in southern constellations have uppercase letter designations, like B Centauri and G Scorpii.

These letters were assigned by later astronomers, notably Lacaille in his Coelum Australe Stelliferum and Gould in his Uranometria Argentina.

Within each magnitude class, Bayer made no attempt to arrange stars by relative brightness.

In addition, Bayer did not always follow the magnitude class rule; he sometimes assigned letters to stars according to their location within a constellation, or the order of their rising, or to historical or mythological details.

)[6] Bayer then repeated the procedure for the stars of the 2nd magnitude, labeling them from gamma through zeta in "top-down" (north-to-south) order.

Although Bayer did not use uppercase Latin letters (except A) for "fixed stars", he did use them to label other items shown on his charts, such as neighboring constellations, "temporary stars", miscellaneous astronomical objects, or reference lines like the Tropic of Cancer.[7]: p.

131 Ptolemy designated four stars as "border stars", each shared by two constellations: Alpheratz (in Andromeda and Pegasus), Elnath (in Taurus and Auriga), Nu Boötis (Nu1 and Nu2)(in Boötes and Hercules) and Fomalhaut (in Piscis Austrinus and Aquarius).[7]: p.

23  Bayer assigned the first three of these stars a Greek letter from both constellations: Alpha Andromedae = Delta Pegasi, Beta Tauri = Gamma Aurigae, and Nu Boötis = Psi Herculis.

[9][10] A further complication is the use of numeric superscripts to distinguish neighboring stars that Bayer (or a later astronomer) labeled with a common letter.