Nightphotography - ND Filter Question?

[Tired but willin]

This may be a really stupid question but I thought I'd ask it anyway. I've recently found some great subjects to try a little star trails with but have needed to take fairly short exposures (2mins) due to the light pollution from a near by town. Is there a possibility that a ND filter could be used so I can reduce my shutter speed and increase my exposure times letting less pollution in? I currently don't own any so can't try out the theory.

Thanks in advance for any help.

 

[Jarmo]

Why don't you just stop the lens down?

I have taken 45 min exposures with no ND filters without a problem. There's really no way to get rid of the light pollution though, unless you find a "cleaner" place.