NEWT 2.5 is a free ray-tracing application that allows the user to layout a classic newtonian telescope. Thanks to some guidance from others more experienced than myself I was able to use NEWT to ensure that the 100% illuminated area being cast by the optics would fully cover my CCD chip. This is arguably the most critical attribute of a true astrograph. In my case I needed a 100% illuminated area of at least 28.11mm (1.11 inches) in diameter. In this case I needed a 2.6" minor axis for the secondary mirror in order to project a 100% illuminated area of 1.3", just lslightly larger than needed.