Revised designations 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). Bayer assigned the first three of these stars a Greek letter from both constellations: , , and . (He catalogued Fomalhaut only once, as Alpha Piscis Austrini.) When the International Astronomical Union (IAU) assigned definite boundaries to the constellations in 1930, it declared that stars and other celestial objects can belong to only one constellation. Consequently, the redundant second designation in each pair above has dropped out of use.
revised designations 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) bayer assigned the first three of these stars a greek letter from both constellations   and  (he catalogued fomalhaut only once as alpha piscis austrini) when the international astronomical union (iau) assigned definite boundaries to the constellations in 1930 it declared that stars and other celestial objects can belong to only one constellation consequently the redundant second designation in each pair above has dropped out of use