I don't know anything about Celestia. However I have been using Starry Night for about 5 months. I also have the Deep Space Explorer which I play with once in a while. The Deep Space Explorer is astonishing. You can set your course and speed ( Light Speed ) and go visit other galaxies. Trying to find your way home in orbit around earth is an interesting challenge. Starry Night has really done an excellent job with this software. <br /><br />Starry Night is my primary learning tool for navagating to deep sky objects with my telescope. I usually select the object targets ( Messier ) or double stars, and memorize the star field around it. I can zoom in to about magnitude 14 if I need to. I easily found Uranus and Neptune using this method. I can go out any night with a 10x50 binoculars and point these faint points of light out. <br /><br /> The most dramatic display of the accuracy of Starry Night occured about two weeks after I started using it. After I downloaded and updated satelite and asteroide information, I noticed the International Space Station rise on the Southern Horrizon ( I had the satelite label turned on ). I turned on the trajectory and noted it would pass near the big dipper. I ran outside with binoculars and there is was, very bright and right on time. <br /><br />The software is incredible. You give it your latitude and longitude. It uses your computer clock time and gives you a real time sky. You can move forward or back in time for many thousands of years. You can also change our point of location to other locations on earth or any other planet. <br /><br />There are too many features for me to describe. Yes it worth the cost. <br /><br />Bill