| Abstract | Twenty-one centimetre neutral hydrogen measurements of NGC 4151 show that the position angle of its major axis is 260 30 rather than the generally adopted value of 1300 derived from the brighter isophotes. Also the inclination is 260 + 80 which makes it more face-on than previously believed. Neutral hydrogen extends 9' arc along the major axis and has a normal surface density for a Sab galaxy in the regions where the outer optical spiral arms are extremely faint. Some implications of these results are discussed. |
