Reports the NYTimes:

“Battle of the Smithsonian” got a major boost from Imax showings, which accounted for about $5.4 million in ticket sales, or roughly 8 percent of the box office over the four days. In an unusual twist, a pair of screens that alternated “Battle” with conventional museum fare at the real-life Smithsonian Institution in Washington had $119,000 in sales for the four days, the best performance of any theater in the United States, said Greg Foster, chairman and president of Imax Filmed Entertainment.

Also of note in the article, the PG-13 rating is used as an excuse for why Terminator: Salvation did not win the box office this weekend:

“Terminator Salvation,” directed by McG and starring Christian Bale, was independently produced, with Warner Brothers and Sony Pictures Entertainment splitting its distribution around the world. The film suffered a bit from having no Imax version: demand for the big screens has outstripped supply of late. It might also have been hurt by televised basketball playoffs that drained some of the young male audience, and the PG-13 rating, which suggested that it was less rough than its predecessors in the long-running “Terminator” series.