Lucky camera, Palomar telescope takes sharper space photos than Hubble

William Atkins
Tuesday, 04 September 2007 20:35

Science - Space

The Lucky Imaging System (“Lucky”), developed by U.S. and U.K. astronomers, uses a new adaptive optics system, which is able to take out much of the distortion from Earth’s atmosphere,  in order to produce some of the best digital images from ground telescopes.           

In fact, the website of the Lucky Imaging team states, “In the absence of the Earth's atmosphere, a telescope will produce sharp images of stars. Our atmosphere degrades this image—small variations in density on millisecond timescales cause the starlight to be deflected, and the images become a bit fuzzy. By using a high-speed camera, and choosing those images least affected by the atmosphere and combining them, we can form a higher resolution image than just adding all the images together.”

The fluctuations of Earth’s atmosphere occur in the range of tens of milliseconds. Such variations degrade the quality of images. However, the Lucky team uses a high-speed camera (twenty frames per second or faster) so that special computer software selects only those images that are least affected by the atmosphere.

The camera is able to perform with such high efficiency due to the use of L3Vision charge-coupled device imaging sensors by the company e2v, which are so sensitive that they are able to detect a single photon.

A group of these images are then combined to produce a much higher resolution image, a system that they call “Lucky imaging.” Thus, the Lucky system performs these high resolution images of astronomical objects by using a very sensitive light-detection system and equipment that detects the variability of atmospheric distortion.

The Lucky team of astronomers is from the University of Cambridge, United Kingdom, and the California Institute of Technology, United States. They are using the Lucky system on large Earth-based telescopes such as the 200-inch (5.06-meter) telescope at the Mount Palomar Observatory in California, the 100.8-inch (2.56-meter) Nordic Optical Telescope (NOT) at the Roque de los Muchachos Observatory on La Palma, Canary Islands, and the 141.7-inch (3.6-meter) New Technology Telescope (NTT) at the La Silla Observatory in Chile.

The inventor of Lucky is Craig Mackay of the Institute of Astronomy at the University of Cambridge.

When the astronomers attached the Lucky system to the PALMmar Adaptive Optic (PALMAO) system, they found that its resolution was about twice as good as with the Hubble Space Telescope. Without the Lucky camera attached, the reflector telescope at Palomar is, on average, about ten times less sharp and detailed as the Hubble Space Telescope.

When attached to the Palomar telescope, the astronomy team says that the images so far obtained are the “highest resolution direct images, about 50 milliarcsec FWHM [full width at half maximum], ever obtained either from the ground or from space in the visible at about twice the resolution of the Hubble Space Telescope.”

So far the Lucky team has released images of the globular cluster M13 (also called “Great Globular Cluster in Hercules” and “Messier 13”), which is over 25,000 light-years from Earth, and planetary nebula NGC 6543 (“Cat’s Eye Nebula”), which is about 3,000 light-years from Earth.

Photographs of these two objects appear at http://www.ast.cam.ac.uk/~optics/Lucky_Web_Site/ and http://www.sciencedaily.com/releases/2007/09/070904082539.htm.

The Lucky Imaging team includes: John E. Baldwin, University of Cambridge; Graham Cox, Nordic Optical Telescope; Nicholas Law, California Institute of Technology; Craig D. Mackay, University of Cambridge; Frank Suess, University of Cambridge; Robert N. Tubbs, MPIA Heidelberg; Peter J. Warner, University of Cambridge; Keith Weller, University of Cambridge; and Sijiong Zhang, University of Cambridge.