Western sky

Line traces of the stars in the north-west sky of the northern hemisphere

The western sky is that half of the starry sky that extends from south to west to north . This corresponds to an azimuth of 180 ° to 360 °. The western sky thus covers a quarter of the entire celestial sphere .

The term is important for astronomy and geodesy insofar as all the stars "sink" on the western half of the sky . The decrease in elevation angle (or increase in zenith distance ) occurs more or less obliquely, which is a consequence of the celestial coordinates ( declination ) and the parallactic angle (see also Greatest Digression ).

This influences the measurement of star passages and the choice of the most suitable instruments for the measurements .

See also: star orbit , earth rotation