Pluto and smaller, dimmer Charon, as seen from the 8-meter Gemini North Observatory atop Mauna Kea on the island of Hawaii.

Gemini North Observatory/NOAO

You still have to wait until 2015 to see Pluto up-close and personal, but astronomers have produced the best picture ever taken of the distant ice-ball from a telescope on the ground.

The image allowed the astronomers to precisely measure the size of the former ninth planet and the distance between it and its companion, Charon.

That’s useful information for the approaching New Horizons spacecraft, which will make NASA’s first visit to the dwarf planet in 2015.

It wants to know where Pluto’s companion Charon and its four tinier, known moons will be, and whether to expect other objects in the vicinity.

“It’s already being used by the experts to define the orbits,” said astronomer Steve Howell, who led the team that captured the image in a half-hour observing run on the Gemini North Telescope on Mauna Kea in Hawaii.

The team made good use of its small window, collecting a series of snapshots at the rate of 1,200 per minute, with a camera called the Differential Speckle Survey Instrument (DSSI), which can remove the blurring effect of the atmosphere.

“If you take an image quickly enough, the blurring of the atmosphere is frozen,” said Howell.

The instrument then combines the images, removing all the random light caused by the atmosphere and allowing only the constant light from the object itself to remain.

Howell, had used the instrument on the WIYN Telescope on Kitt Peak for three years, before leaving his job there to join the science team of NASA’s Kepler Space Telescope in its search for habitable planets orbiting distant stars.

That was the primary reason Howell took the instrument to Hawaii — to test its usefulness for the Kepler mission.

“This was kind of a side project to see how well we can do,” he said.

Howell said the technique can now be used on the stars Kepler has identified as potential hosts to Earth-like planets. It will allow astronomers to rule out the possibility that the diminution of light recorded by Kepler is not caused by a second, or binary, star.

The imaging team included Elliott Horch of Southern Connecticut State University where the instrument was developed, Mark Everett of NOAO and David Ciardi of the NASA Exoplanet Science Institute at Caltech.