 " The Impossible Astronaut " and " Day of the Moon " were designed to be a darker opener to the series and were partially filmed in the United States , a first for the programme . Moffat was keen on incorporating Area 51 , the moon landing , and President Richard Nixon ( played by Stuart Milligan ) into the plot . The episode received final viewing figures of 7 @.@ 3 million in the UK . It received generally positive reviews from critics , though many worried about the number of questions that had been left unanswered . 
