Observations et etude morphologique des nebuleuses annulaires EN (OIII).

A photometric study is presented of the morphology of forbidden O III emission from 10 ring planetary nebulae. Observations were made in a narrowband interference filter centered at 5007 A for the objects NGC 40, 1514, 2392, 6543, 6781, 6826, 7354, 7048, 7009 and 7662, and used to obtain values for the major axis, the distance separating two successive maxima of the photometric profile, the ring/center intensity ratio and eccentricity. These parameters are found to be consistent with a shell model for most of the nebulae, although it is noted that the model only applies to the O III distribution. Fine structure is also found in certain nebulae, indicating the presence of more complex structures to which the shell model is only a first approximation.