iambenben: yes I used tripod, this is must since the exposure is always above 1 sec.
6inch: did not see your post recently
joni: the first patch were in petri island, the second path were taken in shirley's bay, west of ottawa.
fad: my spot meter is still on the road, i should get it soon.
I used reversed GND, but still have some issues, I will try more in coming weekes.
I also found the picutres are over-saturned. My monitor is not good any more, can not calibrate properly, I should consider changing it now.