http://www.wodaski.com/wodaski/pick_a_camera.htm is a good page to start.
I'm not sure on the spec's of the 20Da, but for a 350D (which surely must be similar) you would be at 0.56 arc sec/pixel, which is very small (most people say to aim for 2 arc sec/pixel). So you're doing very well to have such a sharp image there.
For the 350D: 6.4 x 6.4 micron pixels and 3474 x 2314 pixels.
Anyway, it all just proves you've done very well to get such a nice image of this small object
Roger.