NGC 4151 : Sy2 in a deep photometric minimum.

UBV photometric observations of the nucleus of the Seyfert galaxy NGC 4151 obtained using a photon-counting photometer with a 27-arcsec diaphragm on the 60-cm telescope at the Southern Station of Shternberg Astronomical Institute during 1980-1984 and spectroscopic observations obtained near H-beta at dispersion 10-nm/mm using an image tube at the Cassegrain focus of the 2.6-m Shain telescope at the Crimean Astrophysical Observatory during the same period are reported. The minimum of April 1984 is found to be associated with a 2.5-fold drop in the ratio of W-lambda (H-beta) to W-lambda (N2), to a value (0.3) normally associated with Seyfert 2 galaxies, over about 3 months. The Seyfert 2 classification (as opposed to the previous Seyfert 1-1.5 classification) is supported by the color indices B-V = 0.92 mag and U-B = -0.05 mag.