Oh I miss-read years instead of light years. My bad. I'll repost when I've taken that into account.
So bearing in mind that the journey is 10 light years in length as seen from earth we calculate as follows.
The time taken for journey as measured by the observer on earth will be 20 years. And the time taken for the journey as measured by the traveller's clock will be 17.32 years.
EDIT: so szecs post #9 was the first correct calculation, unless I missed some edits. But then iirc he edited post number #7 so that that is now seemingly the first one.
EDIT: Anyway, good to have two separate confirmations of the result. :]