I now keep the temperature of the 300mm lens constant (20C) with two Kendrick dew heaters and a thermostat. Focus does not change with any change in ambient temperature. In fact it does not even change from one night to the next as long as the fridge and lens are at their set temperatures.
Guidemaster has this nifty ability to move your mount in between exposures while guiding. It is set by specifying a radius in pixels of your guide camera. I now control the cameras shutter with Guidemaster by means of a relay box which also does the guide control. Shoestring has USB adapters that do this.
Here is an animated GIF of nine cropped jpg (8min at f5 and 400ISO)images of the same sensor area straight out of the Canon 5DH. You can see the hot pixels are not moving. This of course means when you median stack a set of images signal to noise is even further enhanced. Resolution is also increased depending on how you process.
Animated GIF 4MB
http://d1355990.i49.quadrahosting.co...5/dither01.gif
Some resulting images
Carina 9MB
http://d1355990.i49.quadrahosting.co...5/cardith1.jpg
Rho region 5MB
http://d1355990.i49.quadrahosting.co...05/rhodith.jpg
Swan and Eagle nebs 6MB
http://d1355990.i49.quadrahosting.co.../swaneagle.jpg
The other nice thing now, is that I can set four different exposure lengths with different numbers of exposures. Very handy for HDR data aquisition. If there is no chance of cloud I can then have a long nap while the data collects.
Bert