ER Vulpeculae (HD 200391) is a long turn project star at Nightwatch. This star is an eclipsing binary belonging to the short period RS CVn group.

ER Vulpeculae was discovered in 1946.

From Hall, 1976 comes the following principal characteristics that make this class so interesting; features that can be interpreted as flare like activities; a dampened oscillations at certain orbital periods; variability of the light curves on several time scales; significant period variations both positive and negative.

Photometry of the irregularities of ER Vulpeculae are interpreted largely in terms of spot distribution. Star spots, or as we term them for our sun ... sun spots.

ER Vulpeculae is an important binary because the physical characteristics of the stars (mass, temperature, and radius) are nearly identical to those of our sun, except that the star rotates nearly 40 times faster and has extremely high levels of chromosphere and coronal activity. Thus; chromospherically active stars. I believe that ER Vulpeculae is a very interesting target star for those interested in photometry.