The Canon tentacles. One can simplify things by using an internal battery and capturing on an internal flashcard. But you really need to be able to check focus on a PC monitor. With the Astronomik UHC filter in place (necessary at my light polluted location), M27 is also totally invisible in the viewfinder. Totally black viewfinder, no nebula, no stars. The software ImagesPlus is great for checking focus, and in this case absolutely required to verify the framing. I needed a 2-minute exposure just to see where M27 was. Actually it's possible to achieve good focus on a bright star (I used Vega) just with the Angle Finder C and Viewscreen I (clear center + crosshairs). Problem is, you cannot see the crosshairs in the dark. Trick is to focus the Angle Finder on the crosshairs in daylight and tape it fixed. The very shallow depth of focus then forces your eye to automatically rest at where the crosshairs are. Trying to focus on the groundglass is simply too coarse. The cable release (Canon Timer Remote Controller TC-80N3) makes it possible to program tens of exposures and simply walk away for a couple of hours.