The eclipsing binary star
system V566 Ophiuchi was discovered and classified by Hoffmeister (1935, 1943).
This W Ursae Majoris system was studied photoelectrically without a filter by
Fresa (1954), while Binnendijk (1959, 1965) made observations at hte effective
wavelengths of 4220 and 5300 ?. The unusual stability of this system was
indicated by Bookmyer (1969), whose light curves could be superimposed almost
perfectly onto those observed by Binnendijk nine years earlier. Bookmyer also
confirmed that the secondary minimum is a total eclipse, and determined a new
set of light elements based on a fourteen year interval of observation. From
these observations, which are summarized in the above publication (Bookmyer
1969) she concluded that V566 Oph had a constant orbital period from 1952 to
1966. More recent epochs of minimum light have been published by Popovici
(1971) and Pohl and Kizilirmak (1970, 71, 72). In light of the unusal history
of this W Ursae Majoris system, the authors obtained some further observations.