For an observatory which observes the night-sky day after day, it is important to have good weather throughout the entire night. This is an all-sky scene of a clear spring night as seen by the Okayama Astrophysical Observatory sky monitor. As stars make their daily rotation around the north celestial pole, their light-trails stretch from east to west. The lights that run in straight lines with different directions from the stars and appear for only short periods of time are airplanes flying across the sky. The light surrounding the image low in the sky is the bright glow of artificial illumination from the Setouchi industrial district and extensive urban development. This light pollution creeps into even leading-edge domestic astronomy observations which peer into the abyss of outer space.

Overview of the Starry Sky

In this all-sky image, north is located at the top of the image. Moving clockwise, the western (right), southern (bottom), and eastern (left) portions of the sky are all visible at once. On this spring night, the transition from the winter constellations to the summer constellations is branded into the progression.

On the right side of the image, the bright light sinking into the west is Jupiter. Lined up next to it are Pollux and Castor in the constellation Gemini. In the southwest is the Great Winter Triangle. As the stars which adorn the winter night sink into the western horizon, the constellations of spring move to the center of the sky.

In the center of the image, the bright star moving from the zenith towards the west is Regulus in the constellation Leo. In the northern sky, the light-trails of the seven stars of the Big Dipper (Ursa Major) crowd close together. Following the ‘Great Spring Arc’ extending along the direction of the handle you find the radiance of Arcturus, in the constellation Bootes, and Spica, in the constellation Virgo, cutting across the sky.

In the upper left, the pale-blue light rising in the north-east is Vega in the constellation Lyra. By dawn, the early spring constellations are reaching high overhead.

Watching over the course of one night, we understand that the North Star also traces a small arc centered on the north celestial pole.

(Author: Naito Seiichiro (Public Relations Center))