I am just wondering why you are still taking 1 minute exposures when you are guiding and have a LPS filter. From Glebe with a 400 D unmodded and an astronomic UHC filter, guided with PHD i could go at least 5 minutes.
Paul, I use 1 min subs to reduce the number of subs (i.e. amount of data) that I discard due to minor tracking errors (i.e. I discard star-trailed shots).