Hi
Yes great shot there.
I can now say that doing only one very long exposure is NOT the go. Last night while testing my mates Lumicon Coma Corrector I did a single 30 minute ISO 200 shot of the Lagoon, the result was dissapointing. I got inner detail ok but the outer parts were quite noisy and flat looking, so I think that we should take at least 2 preferably more shots at a higher ISO. I may go back to using ISO 1600, and take 4 shots 10 mins each rather than ISO 800, 20 mins like I have done. A mate points out that if something goes wrong, its better to stuff a 10 minute shot than a 20 minute one
As for exposure I try to get the histogram peak about 1/3 to no more than 1/2 the way along from the left. Less than that is too dark, more is getting overexposed.
Scott