Welcome, Lincoln! I think you're the guy famous for those
beautifully colourful star trails images, right? If so - great work!
The two main culprits for trailing are usually (1) polar misalignment, and/or (2) flexure of your tripod, mount head, etc.
When I used an Astrotrac mount (similar to a Polarie but slightly beefier), I used drift alignment with LiveView to tweak the polar alignment. I was able to take 3 min exposures @ 135 mm (6.4 um pixels) without star trailing. However, you'd need a very stiff tripod - otherwise it flexes when you point the camera elsewhere in the sky, ruining the polar alignment - and a wedge/geared head that lets you tweak altitude/azimuth separately for drift alignment.
Here's an example of a single-shot Milky Way that I took last year: 15 min with a Canon 5DmkII + 14 mm f/2.8L @ f/8 ISO 1600.
http://www.iceinspace.com.au/forum/s...ad.php?t=92443
By the way, if your aim is to create a very high resolution panorama of the Milky Way, you'll get much better results by stitching together lots of panels - each shot by stacking many individual photos together. Here are two of the best Milky Way panoramas that I've ever seen:
http://sguisard.astrosurf.com/Pagim/GC.html
http://skysurvey.org/about/
Broadly speaking, shooting at ISO 100 on a DSLR won't get you as good a result as stacking multiple higher ISO shots of equal/longer duration because there will be more thermal noise, more read noise, stars will bloat and lose their colour from individual pixels being over-saturated, and if you're shooting very wide field - you may run into problems with air glow and atmospheric refraction.
Just as a comparison, here are a few images that I shot just a few weeks before the Milky Way at 135 mm - you'll see that they're much richer with the stacking:
http://www.iceinspace.com.au/forum/s...ad.php?t=91077
Anyway, please take this with a grain of salt... I barely know what I'm doing
Good luck!