U, B, V, J, H, K photometry, polarimatry and spectroscopy of this peculiar object was made from August 1979 to December 1980. During 1979 it was at a phase of stable maximum brightness with variations of less than 0m.2 in magnitude and less than 0m.1 in colour. A change occurred at the beginning of 1980;the object was 0m.5 fainter in mid March and then faded rapidly. During the rapid fading the object became redder in U-B and B-V, and there was an intrinsic polarization of about 1%. At minimum in September 1980, B-V become even bluer than at maximum, while the 1.2-2μ flux was twice lower in October 1980 than in April 1979. At maximum the spectrum was of type F; the Ball lines indicating a luminosity higher than that of a normal supergiant.