"Proper motion" refers to the apparent movement of a celestial object, like a star, across the sky over time. It is caused by the object's actual motion through space relative to our own position on Earth. Full definition
One of the key science drivers for the extension was the study of proper motions of stars in dwarf galaxies, which requires observations taken over as long a time baseline as possible. (astronomynow.com)
The cartoon like graphics make the game very light hearted, it wouldn't have the same feeling if the environments were more serious and sinister with proper motion captured characters and detailed graphics. (thisisxbox.com)
Long exposures are going to let you capture still photos with proper motion blur. (techradar.com)