I've tried this one and it didn't work out well for me. Now I've been doing some reading and some people crank up their ISO really high for this. Is the worry about Noise not there since your add dark frames anyways? (About want ISO should I be around? Another problem i've been having is that once I started stacking the photo's and the end result wasn't seemless and didn't really stick out like alot of people's pictures that i've seen.