We present an observation of the edge-on Sb galaxy NGC 891 taken by Ultraviolet Imaging Telescope during the ASTRO 1 mission with a broad mid-UV filter with half power points at 1800 \AA\ and 3100 \AA. We compare the emission seen in this image with the emission seen in the ground--based optical H$\alpha$ and [S II] $\lambda\lambda$6717,6731 images of Rand, Kulkarni and Hester (ApJ 362 , L1--L4).
The mid-UV emission is brightest along a thin plane corresponding to the major axis of the galaxy. The mid-UV surface brightness of the disk, measured with the center of the galaxy masked out, has a scale height of 0.6 kpc. Emission in the disk is asymetrically concentrated to the NE of the galaxy center, in rough correspondence with the H$\alpha$ emission from young star forming regions.
Diffuse mid-UV emission is detectable in the halo; there are no obvious discrete features, although the signal to noise is low. The emission in the bulge has a scale height of 1.7 kpc, which is in good agreement with the H$\alpha$ scale neight of 1.4 kpc. There are no strong emission lines in the mid-UV band, however, so the radiation here is probably dominated by dust scattering of light from the disk. The halo gas appears to contain significant amounts of dust.
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