I too am getting really excited about this one. Using sparkocam and Oovoo i managed to live stream the moon yesterday in near HD to two friends in Brisbane...my two astro friends in england are super keen to see my stream now on eclipse night! Brisbane weather is looking clear too
RE crop sensor, an APS-C sensor is physically smaller than full frame. Hence you are only sampling a 40% fraction of the image circle produced by the lens, whereas a full frame sensor samples the entire image circle.
Hence you have an effective magnification of 1.6x a full frame sensor. The bulk magnification comes from the lens focal length eg 500mm = 50x.
A full frame sensor is 36x24mm.