Hi John
As others have said, a ball mount mounted on top of the scope or mount will allow you to level the horizon, and as Andrew said, take two exposures and merge them in post-processing to avoid the foreground being blurred.
Here's an example I did of this a few years ago:
http://www.mikesalway.com.au/2009/02...the-milky-way/
I took 1 exposure with the tracking off, and 1 with the tracking on.