I purchased this home planetarium: http://www.segahomestar.com/Sega_Homestar_Planetariums/Homestar_Extra.html" [Broken] It is meant for home use so it is designed to project on to a flat ceiling. Now I want to project it onto the dome indicated in the picture. The problem is it's too small. Only places near the top is illuminated (refer to image). I want to use some optical elements to make it such that more (ideally all) of the dome is illuminated. I'm thinking of using a concave lens. I have some questions: Will a single concave lens work or do I need multiple lens elements? I know that there will be distortion, but how bad is it going to be? Can I somehow fix them? What else do I need to consider? Are there any alternatives other than using a lens?