The best way to take planetary images with the Canon DSLR system is by recording the Liveview at 5x zoom through a USB cable directly onto a computer. Recording movies inside the camera leads to a lower quality image because of the compression used inside the camera - the 5x zoom in Liveview records the pixels at 1:1 (or close to) resolution, and you end up with a series of jpgs at 99% quality level in an avi file. A good description of the process is
here, and Backyard EOS allows you to do this quite easily. Unfortunately the sensor size is quite small at 5x zoom, just 1024x680 for the 600D, which I reckon will be very difficult (if not impossible) to manually point and keep the target in frame.
I used this process last year with my 700D and Celestron Evolution and 6" SCT, but since I was able to track the planet with my mount I was able to get reasonable quality
results. I've since upgraded to a C9.25" SCT and ASI224MC planetary camera, but learned a lot with my 700D.
And like Ross says, AS!3 is more usually used for stacking.
Andrew