NIght Panorama

SO i tried to take a night panorama...and made sure my camera settings stayed the same for both shots..however the light was really differnt from the right pic to the left pic and some pretty bad differences showed up when i mergered them...SO...my question is...should I try and compensate for light differences while I am shooting? or try to match them using PS or something else by just brighting one photo or darkening another? Or is there a good photo stitcher that can detect and compensate for what has happened below??
Shooting Date/Time
8/3/2009 21:25:47
Tv(Shutter Speed)
30Sec.
Av(Aperture Value)
F8.0
Metering Modes
Evaluative metering
Exposure Compensation
-1 1/3
ISO Speed
100
Lens
EF70-200mm f/4L USM
Focal Length
70.0 mm

http://backup.cambridgeincolour.com/...7558/panov.jpg