Deepest deep-space photo ever taken

Using the Hubble Space Telescope's new Advanced Camera for Surveys (ACS), astronomers have taken what is said to be the deepest visible-light image of the sky ever captured. At left: at detail from the ACS image with a few bright Milky Way stars in the foreground, framed by faint stars in the halo of M31 and far-away galaxies. From the Sky and Telescope article:

"The 3.5-day (84-hour) exposure captures stars as faint as 31st magnitude, according to Tom M. Brown (Space Telescope Science Institute), who headed the eight-person team that took the picture. This is a little more than 1 magnitude (2.5 times) fainter than the epochal Hubble Deep Fields, which were made with the Hubble's Wide Field and Planetary Camera 2. It is 6 billion times fainter than what can be seen with the naked eye."

link, Discuss, (Thanks, JP!)