A map of the northern sky at 10 MHz.

The Penticton 10-MHz T-shaped array has been used to map a large portion of the sky north of declination -5 deg; the beamwidth at the zenith is approximately 2 deg. The map includes a portion of the galactic plane, the high-latitude region of minimum sky brightness, and part of the north galactic spur. Comparisons are made with surveys at higher radio frequencies and with optically observed H II regions of large angular size; most of these H II regions give rise to prominent absorption features on the map, and these are discussed in detail. An estimate of the mean value of the emissivity of galactic nonthermal radiation has been derived, and most of the emission is shown to be confined to the spiral arms, with much lower emission present in the interarm region.