Wow! You haven't gotten much serious advice, have you? :( Who knew the pooch could bring out such...passionate...responses. ;)
If you have an "interior," room in your house, place the dog in that room, with their bed. By interior, I mean no outside walls, and no windows. They should not be able to hear outside (i.e., the owl) noise from this room.
If being away from you will result in barking, try putting the dog where it normally sleeps, but put a portable fan near it. This will create white noise, preventing the dog from hearing the owl. Fan should not oscillate, as that affects the noise it produces. Needs to be high speed and steady (pointed away from the dog of course).
Finally, as a training method to stop barking, fill an empty, clean spray bottle with water. Whenever the dog barks, say "NO" in a low, firm voice and spray the dog in the face. It has to be a new spray bottle (reused is too risky because you might not get it clean enough). This was recommended to us in obedience school. Sounds mean, but our Labradoodle learned very quickly. ?Course, our Lhasa Apso was another story...god help you if you have one of those! (laugh)
Good luck.