[Utah-astronomy] Canon Xsi 450D CCD well dimensions - what are

Some misc questions on the Canon XSi 450 DSLR for astrophotography: What are the dimensions of (1) the CMOS sensor and (2) an individual well on a Canon XSi 450D? (3) What is the sensor id used in this camera? (4) With respect to the sensor cleaning function, exactly what is that and how does it work? Assuming that the feature somehow shakes the dust of the chip, do you have to take the lens out really have the sensor cleaned? If you leave the lens in, does the cleaning feature just make the dust float around in the camera because it has no way to exit the body? Thanks, Kurt