I modded my own 1100D sometime back as described by Gary Honis i.e. removed the 2nd filter and left in the IR/UV cut filter. Now I have heard from many sources now that the Canon filter may not be the most efficient for astronomy, therefore I propose the following for anyone yet to mod their camera:
- Disassemble the 1100D and remove the entire filter assembly (black plastic unit holding both filters).
- Pop in an Astronomik CCD CLS clip filter (will also keep dust off the sensor).
- Alternatively use just a CLS clip filter and an additional 2" IR/UV cut.
My thinking is that by doing so the camera should be as good as it can get without adding active cooling etc, also if you ever want to sell on the camera or use it as Canon intended, then all you do is pop the filter assembly back in.