text: The program is based on the Hipparcos Catalogue ( HIP ) and allows users to travel through an extensive universe , modeled after reality , at any speed , in any direction and at any time in history . Celestia displays and interacts with objects ranging in scale from small spacecraft to entire galaxies in three dimensions using OpenGL , from perspectives which would not be possible from a classic planetarium or other ground based display .
simplified: The program is based on the Hipparcos Catalogue ( 120.000 Stars ) and allows users to display objects from artificial satellites to entire galaxies in three dimensions in OpenGL .