Awesome photos! I am wondering how you did the exposure times though, "set it to 15 minutes". Did you use a shutter release cable/remote while its on Bulb mode? I have a t2i and my longest shutter speed is 30 secs then Bulb after that. Or does your camera have a feature where you can jot down a number of seconds manually?
I have am ML-L3 shutter remote, I also have a setting that lets the shutter stay open for 1,5,10,or 15 minutes OR untill I hit the remote again. So I set it to 15 minutes and only used 344 seconds (5.7 minutes) So I think i'm going to try it again but time it this time for 14 minutes or so and get alot more work done

. Check the user manual, i'm not familiar with canon settings sorry. Yes my camera was set to BULB mode. It helps alot.