AAVSO: American Association of Variable Star Observers

Photometry of Betelgeuse Through Its Recent Faint Minimum (Abstract)

Volume 48 number 2 (2020)

Tom Polakis
Command Module Observatory, 121 W. Alameda Drive, Tempe, AZ 85282; tpolakis@cox.net


(Abstract only) Betelgeuse is nominally one of the ten brightest stars in the sky, known to vary irregularly between roughly magnitude 0.3 and 0.8. During December of 2019, it became apparent that it was approaching a historically faint minimum, and at a faster than usual rate of descent. V-band observations at Command Module Observatory commenced on January 12, 2020, and were carried out on 40 nights through April 19, 2020. Since the star is far too bright for measurement with the 32-cm telescope and sensitive CCD detector, an aperture mask and defocusing were required to achieve acceptable ADU counts. Errors associated with shutter timing and scintillation due to the necessarily short integrations were combated by taking multiple exposures of the target, comparison, and check stars. The resulting light curve captured not only the time of minimum, but also showed nightly fluctuations in brightness whose validity appears to be supported by the stability of check star magnitudes.