My old canon T1i worked best at ISO800 for wide angle astrophotography, it's 5 year old sensor and processor tech. I got a new canon 70D, late May, I so love it's more control/etc than my T1i. That tilt screen is a neck saver also, and touch screen ability to change settings is great also for astrophotography. For day use I shoot thru viewfinder. Simply, what are other 70D users shooting wide angle astrophotography with for ISO as balance between light gathering in short time vs image noise? 1600? 3200? Since I can't tell noise on small view screen I'm double shooting many with both, heck 1 64GB card holds nearly 2,000 RAW images, and I'm only on card 1 of 3. My lens is the 15-85 , I simply shoot at 15mm with f3.5, 25 sec max (limit star oblong stretch) always for wide angle astrophotography. As posted elsewhere here I'm actually 2 weeks into a 3 week big family out west vacation, no access to computer. Just iPhone surfing. Camping at Yellowstone canyon campground, 3rd night now. Only get 3G data seems 9pm-6am, then network seems overloaded and 1x rest of day. When back I'll post photos in other thread. Thx in advance.