Hi,
This is info given me by someone else on the forum, and is a rough guide.
Maximum exposure time before trailing is evident isL
t = 1000/FL (near the pole)
and
t = 700/FL
where
t = exposure time
FL = focal length of lens
of course, this is a rough guide.
also, see this thread for what is possible:
http://www.iceinspace.com.au/forum/s...ad.php?t=21306
with 50 x 10 second exposures
and my poor first attempt with 10 x 13 seconds for comparison:
http://www.iceinspace.com.au/forum/s...ad.php?t=23805