This product has successfully introduced thousands of people to the fascination of studying the night sky. Dials around the outside of the barrel are set to the hour and date required, showing the stars and constellations visible at the same time on an accurate, computer-generated disc within. The star map can be referred to through the focusing viewfinder with one eye, whilst alternatively observing the real night sky with the other, making identification quick and easy. Has Latitude compensation rings, northern hemisphere mapping and night illumination. Please note: only works in the northern hemisphere between latitudes of 20 - 60 degrees.