CCD observations of supernova remnants

The high quantum efficiency of CCD detectors makes it possible to study faint features in supernova remnants that are only barely detectable on the longest photographic exposures. The advantages of the CCD over the photographic plate is particularly striking in the near infrared where photographic emulsions are inefficient and where interstellar absorption is much reduced. The fine seeing in Hawaii allows study of much finer detail than was previously possible at other sites. Observations of the Crab nebula in subarcsecond seeing show that the H-alpha filaments in this object consist of chains of stellar or quasi-stellar knots with diameters less than about 1.0 arcsec (0.01 pc). 10 references