Hi Leon,
Hope you are and have enjoyed the SW! Yes, the skies can be quite dark and we have been lucky with the endless summer here although we desperately need rain - it's pretty shocking here at the moment. Low-Mid 30's all next week too.
I have attached this link to a star trails I did recently with my 40D. I found that opening the aperture up too much (ie F4 or larger) caused rapid sky glow to accumulate so I now use F8. Then I can push out to about 4 minutes per shot before noise becomes an issue and then if you're lucky to have one of the programmable remote shutter release units, you can program it to take up to 99 shots to give nearly 6hrs of trails. Then use Startrails to stack them. BTW, make sure you take the dark frame at the beginning as it does make a huge difference. Startrails allows you to register a dark frame.
Good luck and enjoy the rest of your trip!
Cheers,
Darrin...
http://www.iceinspace.com.au/forum/s...ad.php?t=73663