PRECISION VELOCITIES FROM RADIO LINES

Accurate radio velocities are much easier to measure than optical velo cities, particularly when derived from molecules. Thus substantial (10 km s(-1) y(-1)) changes were discovered while simply monitoring 22 GH z water masers near the nucleus of NGC 4258, which is probably in cons equence a massive blackhole. More speculatively, some methanol maser h ot spots in compact I-Ill regions may be associated with proto-planeta ry objects, which would make them amenable to study. It is therefore t imely to look for contributions that measurement of secular velocity c hanges might make to Astronomy. We discuss a methodology and identify several contexts that could be informed by an abundance of intense, na rrow lines, such as those observed from methanol.