In the extreme east is RR Lyrae, the prototype of the large class of variables known as RR Lyrae variables, which are pulsating variables similar to Cepheids, but are evolved population II stars of spectral types A and F. Such stars are usually not found in a galaxy's thin disk, but rather in the galactic halo. Such stars serve as standard candles, and thus are a reliable way to calculate distances to the globular clusters in which they reside. RR Lyrae itself varies between magnitudes 7 and 8 while exhibiting the Blazhko effect. The easternmost star designated by Flamsteed, 19 Lyrae, is also a small-amplitude variable, an Alpha2 Canum Venaticorum variable with a period of just over one day.