You really have to mod your camera as the IR cut is way to strong, if you check my 1100d modding thread you will see the massive change this makes.
http://www.iceinspace.com.au/forum/s...ad.php?t=88886 post 23
At ISO 1600 your really pushing the 1100D in normal temps, try a DIY cooler box. Atm my wife is running hers at iso 800 and just using more subs. If your just using the camera for AP work and run it via usb, you could loose the LCD which would also aid cooling.
As for dust just use an air duster made for electronics and camera before each session, a quick squirt will do the trick. Lol lived at Accia ridge for a bit and I sure know about the dust when it blew in from the in-lands. Your image looks sweet to me wish we had some clear skys tonight in melbourne town
Edit: dam just scrolled down that thing is filthy, have you tried a sensor swab that maybe oil or something?