1986JAVSO..15...15K

This paper presents BV photometry of three SRc variable stars: alpha Orionis, CE Tauri, and mu Cephei, made with careful consideration of the first and second order atmospheric extinction and reddening parameters. Betelgeuse displayed a 0.4 magnitude rise in brightness, peaking on approximately 26 February 1986 (JD 2446488). For Betelgeuse, <B-V> = 1.876 ± 0.014 from 17 differential measurements with respect to gamma Orionis over a span of four months. This is somewhat redder than other published values. On a clear night at the 9200-foot level of Mauna Kea on the Island of Hawaii, the typical V band extinction is 0.15 magnitude/air mass, and the sky brightness at the zenith on a clear night is V = 21.2 magnitudes/square arc second.