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Abstract

Spectra of the Orion Nebula with a long slit (7' and 3' in the sky) and with exposures to the appearance of the visual continuum have been obtained for several positions in the field including, in particular, areas of low surface brightness. The variation of the ratio q = intensity of Balmer emission / intensity of continuous emission is studied. This ratio changes generally rather irregularly along the length of the slit and also from position to position. The spatial variation of q is generally small with the exception of the center of the nebula, where it is particularly high.

The variation of the ratio q can be seen with a much higher surface resolution than in the spectra, when comparing monochromatic photographs taken in H α + [NII] with those taken in the continuum between the stronger emission lines.

Within the larger part of the field of the nebula it is possible to distinguish between surface structures typical of the continuous emission and those typical of the hydrogen line emission. The persistence of this differentiation in many areas below the Balmer discontinuity as well as above Hα in the near infrared proves that for the subareas with the stronger continuum the continuous emission must be predominantly scattered light for the entire wavelength range from the ultraviolet to the near infrared. This criterion cannot be applied to areas where there exist no clear differences in the surface structure of the two types of emission. A determination of the Balmer and Paschen discontinuity may possibly lead to a decision.