http://www.nikonchat.com/nikon-flash-trigger-voltage/

I can use my Nikon flash for Canon offshoe?
I have 2 nikon flashes, the SB-20 and sb28. and I want them offshoe, with my "trigger flash ebay. "i was taken with a Canon, which has a trigger mounted on the shoe. I understand that if I can mount the flash on my Canon nikon, there could be some fixes the shares of the electronics to the difference between the voltages. but offshoe shot, cause a problem? because I'm not really connect the flash and the camera together?
Your Canon is safe. Nikon makes some good flashes, and provided you can put in manual feed mode that will make for great camera flashes.
Nikon SC-29 problem SOLVED! (video does not show solution – read the description for the solution)