Hi Paul.
I had planed to follow Roger Clark's lead and do the following for the 60Da, tho I've never found the time. I'll get there eventually but thought you might like to have a read and possibly give it a go yourself:
http://www.clarkvision.com/astro/can...gnal-to-noise/
Lots of other interesting reading on that site too.
Edit: note that the LCD obviously has less heating effect on the 60Da as it does on other bodies, however prolonged use of live view does increase the sensor temperature, whether you use the LCD or remotely via a PC, so try to use live view sparingly and briefly.