Dual Axis Motor drive & exposure times

[Kevdan]

Hi All,

Can anyone say what is the longest useable exposure time they have been able to get with a dual axis motor drive for a skywatcher EQ3-2 mount,

Im having trouble getting any decent images on galaxies and am trying to cover all bases, I have just polar aligned my scope as best I can and left it for 10 mins and it is still in the small circle in as near as where it was to start with, so Thats probably as good as Im going to get,

Camera is a penatx ist-dl 6.3mp dslr which is slow and takes nearly 4mins to take and process a 1min40sec exposure, but is this exposure length too long for the motor drive or is it a case of lock onto a bright star, then focus using a bahtinov mask, take an as long as possible pic and then view it to see wether it is ok? and then if this is ok just sit back and wait.

Kev.