G'day Mat,
Sorry for the delay, I'm not getting email notifications through at the moment.
You ask "why's that Doug?"
What I had in mind was that assuming the mount and scope are set up initially on a concrete base, and polar aligned. Setting up again out on a field trip where the ground might not be a unyielding as concrete, leveling an unloaded tripod might not be as static as one would want. With the weight of the mount head and scope etc on the tripod one leg could settle more than the others. Leveling using the bubble should always get your polar axis fairly close, leaving only azimuth to need correcting when doing a quick drift align.
I know the bubble is not repeatably accurate for setup after setup however most people don't want to spend all night drift aligning.
hope that clears that up
Someone raised the point that the bubble might not be set in the mount correctly, and that is probably true. I had a quick 5min look at an EQ6 at Bintel recently (I'm obviously now a world expert)
Is that bubble cemented in or might it be easily reset?
Cheers,
Doug