Radio Observations of Planetary Nebulae

Extract

I am to report on a rather extensive series of observations of planetary nebulae, using the Mark-II radio telescope at Jodrell Bank. The method of observation adopted involves comparing the signal received from a beam centered on the nebula with two beam areas horizontally displaced to either side of it. If the source is not too far South, the confusion effects can be reduced by making observations at different hour angles. A second source of error, particularly in the earlier results, arises from the fact that the positions adopted for some nebulae were not as accurate as had been assumed. The anomalously low 6 cm flux for IC418 in particular is now believed to be due to this cause, and can be disregarded.