ABSTRACT
The star α Cygni, `the Tail of the Swan'. One of the three bright stars which form the asterism of the Summer Triangle, with Altair and Vega. It is a white supergiant of spectral type A2Ia, apparent magnitude 1.25. It is a very distant star (approx. 3230 light-years, parallax 0.001''), and is the type-star of a class of pulsating variables, varying rather erratically over a range of ±0
