One of the world’s largest astronomical lenses has been made in New Zealand. It will help power a telescope in the Canary Islands surveying over 10,000,000 heavenly objects, including stars in the Milky Way, and extragalactic sources out to the extremes of the observable universe.
Wellington-based KiwiStar Optics, a business unit of Callaghan Innovation – New Zealand’s innovation agency, recently delivered a set of six lenses, one being 1.1 meters in diameter and will form a new prime-focus corrector for the William Herschel Telescope (WHT) in the Canary Islands. The corrector will feed a new instrument, titled WEAVE (WHT Enhanced Area Velocity Explorer), which involves the intertwining or weaving of approximately 950 fibres at the focal surface. The corrector optics are the result of several years’ work by a team of Wellington-based scientists, engineers and master opticians.
Sandra Ramsay, Manager of KiwiStar Optics, is thrilled with the result. “The delivery of the final lens allows us to conclude what has been a hugely successful project.
“The business unit has a significant reputation globally for its highly-specialised lenses and is working its way through a substantial list of large contracts.
“It’s not widely known outside of astronomy circles that New Zealand has this level of technical expertise and state-of-the-art equipment to create these lenses”.
Dave Cochrane, Team Leader of Optical Manufacturing at KiwiStar Optics and the Project Manager for the WEAVE project explains some of the technical details.
“We bring the glass over from the USA, Japan or Germany and then it is milled into shape using our 5-axis CNC mill. Once in shape the lens goes through a series of shaping and polishing processes to get it within 1 micron of accuracy (a human hair is about 75 microns).
“The final polishing process is done using powders as small as 1 micron, and an accuracy down to 0.05 microns (less than 1000 times smaller than a human hair).
“When both sides of the lens are polished, it is packed and shipped to one of several specialist vacuum coaters in the USA for anti-reflective coating. The lens is then returned to KiwiStar Optics for final testing and inspection before being shipped to the client.”
The complex process and travel required means the lenses take over 12 months to manufacture. Creating the lenses is a collaborative effort and includes input from New Zealand’s Measurement Standards Laboratory (MSL), Callaghan Innovation’s own mechanical workshop and several New Zealand based companies.
Ahead of the team is an active order book of work comprising fabricating more large lenses and building three high resolution cameras for the VISTA telescope in Chile. Furthermore, the business unit is manufacturing collimator mirrors, a large reference sphere, building a spectrograph and providing an additional infra-red spectrum camera to the MAROON-X Spectrograph for the Gemini Telescope. These projects exhibit the depth and breadth of a team working to unlock the universe.
About the WEAVE project:
Background: WEAVE is a new multi-object spectroscopy facility being constructed for the 4.2 meter William Herschel Telescope (WHT) at the Observatorio del Roque de los Muchachos on the island of La Palma. WEAVE will allow simultaneous observations of up to 1,000 targets over a 2-degree field of view, and is designed specifically to provide high quality spectra over a wide wavelength range to complement large-scale imaging surveys from ESA’s Gaia satellite and the European Low Frequency Array telescope (LOFAR). WEAVE will operate for a minimum of 5 years to conduct large-scale surveys of over 10 million astronomical objects including stars in the Milky Way, and extragalactic sources out to the extremes of the observable universe.
The WHT is operated by the Isaac Newton Group (ING) of observatories, a partnership between the UK, The Netherlands and Spain. WEAVE is funded by the ING member nations, together with additional partners in France and Italy, and a number of institutes and individual researchers in Mexico, Hungary, Sweden and Germany.