CELX - Celestia Script is a file extension that can be used for universe browsing programs. You will be able to use this extension with scripting language and also tells you different directions for angle observation. This extension is used for location markings as well in space. You will also be able to create tours of the universe. You will be able to download this extension online when you have time. It does not cost any type of money at all. There are CELX files in which you can design in a plain text format and wrote out in a text editor.