| NGC 4151 (UGC 7166, 1208+3941) -- This is probably the best studied Seyfert 1 galaxy. The archival image is a 900 s exposure with the f/48 FOC in its 512 × 1024 ``zoomed'' pixel mode. The image was taken after the HST refurbishment mission and the installation of COSTAR, and so is free of spherical aberration. The field of view is 28" × 28", .014". The image was obtained with a combination of the F220W and F275W filters, giving an effective peak transmission at ~ 2450 Å. Considering the response of this setup and the exposure time, the image has 1/4 the sensitivity of the standard setup for diffuse sources, but better sensitivity to compact sources because of the improved optics. The bright Seyfert 1 nucleus is strongly saturated. Its brightness cannot be reconstructed, as in Maoz et al. (1995), due to the absence of the spherical-aberration diffraction rings. In addition to the nuclear point source, there is a diffuse-light distribution centered $2" south of the nucleus. Excluding the counts from the central source, the flux from the diffuse component is 1.2 × 10-13 erg s-1 cm-2 Å-1. This value casts doubt on the component's reality, since measurements with IUE, whose aperture would include much of this extended (and presumably non-variable) emission, have been at times up to a factor of 6 lower at this wavelength (e.g., Ulrich et al. 1991). The diffuse component may be an artifact of the poor quality of the f/48 FOC flat-field, or of a dark current in this camera, which has had operational problems since December 1992. The large arc to the west is an artifact.
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