Chemical composition of the filaments in the Crab nebula. I. Observed features in the spectra of the filaments

Published results of spectrophotometric observations of the filaments of the Crab nebula are analyzed. It is shown that the existing differences in the spectra of individual condensations are real. Investigation of the observed variety of the filament spectra leads to a representation of the range of intensities of the spectral lines observed in the filaments by three mean spectra containing the intensities of all the necessary lines. It is shown that a correlation between the lines [0 III]/H/sub β/ and [0 II]/H/sub β/ exists only for the filaments of the Crab nebula and the Cygnus Loop (which is also a supernova remnant) and is not observed for any of the diffuse or planetary nebulas