Alan, it sounds like you have long exposure noise reduction ON. That means your camera will take a 45 sec dark pic for every 45 sec light pic you take. You're better off deactivating it and taking a few separate darks.
I just tested the Sony, it can take a 10 sec pic with virtually no delay between shots.
I'm going to our dark site tonight, glorious blue skies out, I can't understate how excited I am to give this baby first light!
Here's a shaky HANDHELD quickie I took last night with a 200mm lens, at 1/4 of a second, at 12800 ISO. Very pleased. not with the image, terrible, but the noise, sensitivity at stupid exposure times and star colours impress me. At 1/2 a second the light pollution starts to be exposed! So I could try 1200 subs for an hour?
