SkyMapper provides new digital insights for astronomers

The Corrector Lens Assembly is lowered into the Skymapper telescope.

Operated remotely via a 700-kilometre, optical-fibre link from Mount Stromlo in the ACT, SkyMapper is a new generation surveying telescope which is able to scan the skies more quickly and deeply than ever before.

Based at Siding Spring Observatory in New South Wales, it will be used to create a digital map of the entire southern sky using detailed pictures taken over the next five years. Information gathered from SkyMapper, about 400 Terabytes (or 100,000 DVDs worth) of data, will be shared globally among astronomers via the Internet.

Designed and built by ANU’s industry partner, EOS Space Systems (EOS), SkyMapper has risen, phoenix-like, from the ashes of the Great Melbourne Telescope which was destroyed in the Canberra bushfires of 2003.

EOS Executive Director, Craig Smith, says that the new telescope is the result of meticulous planning over the last five years, and involved the commissioning of IRL and its subsidiaries, KiwiStar Optics and Measurement Standards Laboratory (MSL^[?]), to build one of the most critical components.

“SkyMapper’s Corrector Lens Assembly (CLA) is the complex lens system that is used to correct aberration and allows the extra-ordinarily large field of view to be accessed while retaining excellent image quality across the field. It is crucial that the lenses are aligned correctly to extremely tight tolerances, which presented numerous challenges.

“IRL’s combined capabilities meant that the entire process was able to be completed in one place; from grinding and polishing the lenses to our exact specifications, to the precision engineering required to build the anti-vibration housing in which to ship the system to Arizona for testing and assembly into the main telescope.”

Kiwistar Optics workshop manager, Dave Cochrane, says that the detailed planning, optimisation and optical tolerancing put into the design by EOS optics manager and ex-IRL scientist, Andrew Rakich, played a big part in the smooth running of the project.

“The tight tolerances did present challenges; however, with the use of interferometry, an extremely precise way of checking distortions on the lens surfaces,  these challenges were successfully overcome. Using MSL’s three-axis co-ordinate measuring machine to carefully align the completed lenses in their individual lens cells and in turn align these to a common optical axis in the CLA also helped considerably. The whole project took us six months to complete.”

Once the entire telescope had been through acceptance testing in Arizona, it was then disassembled and shipped to Siding Spring Observatory.

Craig Smith says that SkyMapper is also Australia’s most sensitive digital camera and can take images of a patch of sky 25 times larger than the moon.

“SkyMapper has been described as a ‘268 megapixel behemoth’. With sensitivity five million times greater than the human eye, that’s a pretty accurate description.”