Cygnus Without Stars

Explanation: The sky is filled with faintly glowing gas, though it can take a sensitive camera and telescope to see it. For example, this twelve-degree-wide view of the northern part of the constellation Cygnus reveals a complex array of cosmic clouds of gas along the plane of our Milky Way galaxy . The featured mosaic of telescopic images was recorded through two filters : an H-alpha filter that transmits only visible red light from glowing hydrogen atoms , and a blue filter that transmits primarily light emitted by the slight amount of energized oxygen . Therefore, in this 18-hour exposure image, blue areas are hotter than red. Further digital processing has removed the myriad of point-like Milky Way stars from the scene. Recognizable bright nebulas include NGC 7000 ( North America Nebula ), and IC 5070 ( Pelican Nebula ) on the left with IC 1318 ( Butterfly Nebula ) and NGC 6888 ( Crescent Nebula ) on the right -- but others can be found throughout the wide field.