Markus,
I don't know whether you've seen this.......
http://www.iceinspace.com.au/63-499-0-0-1-0.html but I found it to be excellent for aiding alignment of my tripod.
Also I have three different compasses, a Suunto which I've had since working in geology in the 80's, plus two others, I always use all three to cross check for true south.
