(region of sky with little Milky-Way neutral hydrogen)
The Lockman hole is a region of the celestial sphere
which has little neutral hydrogen within the Milky Way,
i.e., fewer than usual HI regions.
It is about 15 square degrees in size, with some variation
in column density across its expanse.
It of interest for extra-galactic observations that would be
affected by such gas.
Referenced by page:
Spitzer Extragalactic Representative Volume Survey (SERVS)