An examination of
photographic plates at the Maria Mitchell Observatory reveals that times and
maxima of NS Cygni, an RR-Lyrae variable, cannot be represented by a single
linear set of elements; the period of this star has changed at least three times
between 1930 and 1990.It has
returned at least once to a previous period, years after it had changed.Elements valid for 1983-1990 are:
JD_max = 2447220.6414 + 0.5503287 E.The period of EP Cygni, a Cepheid variable, has remained constant.Revised elements, valid for 1967-1990,
are: JD_max = 2444003.096 + 4.288963 E.