Hα-wide and narrow-band photometry of R Canis Majoris

H-alpha wide- and narrow-band photoelectric observations of the eclipsing binary R CMa were made at the Biruni Observatory between February 18 and March 2, 1983. The light curves obtained from the observations are analyzed according to Kopal's method for the orbital elements by using frequency-domain techniques. It appears likely that an exchange has taken place on the angle of the first contact and is probably continuing at the present time. New geometric and photometric elements are derived, and a new value for the angle of the first contact is also given. (Author)