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Yes - you just need to set flash in your menu to "control" and then swith the sb-800 to wireless using the settings recommended for your region (mine are C channel) and you use the onboard flash to fire the wireless sb-800 - it's all in the manual.
indeed it is all in the manual (about 125pages). I have read it 10 times, i have tried it 20 times but when I'm in the feeld and I want to use it I still need my manual (or my notes). No ... it is not that difficult but you need to spend some time whit your manuals (both d80 and sb800). It is a complex system. Try al the settings that they discribe at home. You need to learn to use your channels.
You can use your camera as a wireless commander for your sb800.
A help could be, that you write some settings on a card that you will always keep with you on the field, this as a reminder. It will be a great help for the nexts few mounths. After that you will not need it anymore.
The last two can be printed or copied and pasted into a word file and printed out in any size. I've made memory cards for myself from them for those times when I go stupid; have hem in my camera bag as memory joggers.