I use the C-700 as well. I have done some night work with the camera and have had mixed results. I keep in on iso 100, m mode, tripod, and use the auto shutter so I don't move the camera while depressing the shutter button. 16 seconds is a long time, and as you can imagine a certain amount of noise will present itself. I have found it to be almost negligible at exposures of around 5-7 seconds or less as long as there is some ambient light available. I have tried other iso settings but was less then satisfied with the results. Use a mid range f-stop, and bracket, bracket, bracket!
Keep us informed with your progress. And good luck.