I'm looking at the QHY183 cam which comes paired with a small filter wheel holding 1.25" or 31mm filters. I have a 2" focuser on my scope so could upgrade the filter wheel to their 2" or 51mm model but my question is is it necessary to do so in order to cover the sensor, which is 8.9mm x 13.3mm? My 106mm scope has a focal length of 530mm if that figures into the calculation. The back focus of filter wheel + camera is 33mm. I took a stab at a calculation but don't really know how. Thanks.