A high-latitude H I-cloud with optical emission

A high latitude H I-cloud (l ≈ 91°, b ≈ 38°) extended over several degrees on the sky with brightness temperatures T_B ≤ 20K, velocity dispersion s ≥ 1.0 km s^-1 and a centre velocity v_LSR ≈ -21 km s^-1, has been observed with the 100 m telescope. The cloud is found to be in detailed positional agreement with a faint diffuse nebula visible on the red and the blue prints of the Palomar Observatory Sky Survey. Estimates of the extinction in the nebula from star counts indicate that the ratio of H I column density to extinction is about a factor of 10 smaller than the standard value found from UV-observations.