A new look at the interstellar hydrogen through a very-wide-field photographic Hα survey of the whole Milky Way.
In order to extend the limit of detection of the general H emission in the galactic plane, a photographic survey was carried out with a new, 60" field, high luminosity camera using a very narrow interference filter centered on H . A mosaic of fourteen wide-field H plates is presented. This atlas sums up, as completely as possible, the H emission features for the entire Milky Way. The limiting emission measure is estimated to be less than 30 pc. General, diffuse Ha emission is detected throughout the inner Sagittarius-Carina arm, and is found to be present in the Perseus arm. The survey reveals a number of new large-scale regions of faint emission. They are catalogued and described. The survey also reveals unsuspected filamentary extensions of the Orion complex. Key words: galactic diffuse Ha emission - HIl region - very-wide-field, interference filter camera
Astronomy and Astrophysics Supplement Series
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