out at (some place)
At a location or event outside of or distant from (one's house, office, current location, etc.). The boss it out at a meeting across town at the moment. Would you like to leave a message for her? John is out at bar with his friends tonight.
out at some place
located at a distant place. Tom's out at the farm and there's no phone there, so you can't talk to him. Jed is out at the cabin on a hunting trip.