Mike,

From memory it was either 4 sec or 5.7 sec exposures... but I'm leaning more towards 5.7 sec exposures.

That's correct the LPI can take up to a 16 sec exposures. Personally I think exposures above the 8 to 10 second mark you start to introduce allot of noise with the LPI... probably part of the reason it's not generally used for dso's

regards