The peculiar supernova remnant CTB 80

Deep CCD exposures of the peculiar supernova remnant CTB 80 in the light of the Hα+ [NII], [SII], [OII], and [OIII] filters have been obtained. These images reveal significant shock heated emission in the area of the remnant. An extended bright diffuse nebula in the south–east part of CTB 80 overlaps soft X-ray emission from ROSAT but it does not appear to be related to the remnant under study. New diffuse and filamentary structures are detected to the south, south – east, and north of PSR 1951+32 most likely associated with CTB 80. Especially, the sulfur line image shows emission in the north along the outer boundary of the IRAS and HI shells. The [OIII] emission is filamentary suggesting shock velocities greater than 100 km s but its spatial extent is quite limited. Lower shock velocities are expected in the north and north–east areas of the remnant, since [OII] emission is present while [OIII] line emission is not detected. The comparison between the [OIII] and [OII] line images further suggest the presence of significant inhomogeneities in the interstellar medium. The flux calibrated images do not indicate the presence of incomplete recombination zones, and we estimate that the densities of the preshock clouds should not exceed a few atoms per cm. The typical projected