A new mirror currently being integrated into the University of Tasmania’s Greenhill Observatory will further facilitate the tracking of celestial events near and far.
The University operates an optical observatory at Bisdee Tier in the Southern Midlands. The centrepiece of this facility is the 1.27-metre Harlingten telescope.
One of the largest in Australia outside of the Siding Spring Observatory in NSW, Greenhill was commissioned in 2013 and has since contributed to studies of Pluto’s atmosphere and the discovery of planets around other stars as well as to a just-published polarisation study.
The original telescope had been donated by Caisey Harlingten, an amateur Canadian astronomer, who became aware of the existence of its 500kg primary mirror, in a Vancouver warehouse, in 2004. The mirror had been cast in the US in 1970 and figured in Canada, and intended for use at the University of Tasmania’s Mt Canopus site. The planned observatory expansion did not proceed and the mirror was placed in storage.
However, soon after the telescope entered service, School of Natural Sciences staff discovered an optical flaw in the primary mirror, one that prevented it from being used to its full sensitivity.
“As with NASA’s Hubble Space Telescope, errors during optical testing had left the mirror needing a drastic correction to its prescription to produce high-quality images. An analysis revealed that to order a replacement mirror from a Canadian optical firm was the most cost- and time-efficient solution,” Associate Professor Andrew Cole said.
“The new mirror differs from the old one in being designed to be very lightweight, using an experimental manufacturing technique that supports the mirror on glass posts, with many gaps for airflow and weight reduction. It weighs ~180 kg, about one-third of the old mirror.”
The replacement arrived in Tasmania via air freight in early March, and staff members have been working to integrate it with the optomechanical structure of the telescope and verify its performance.
“Once this work is complete, the rejuvenated telescope will be ready for another season of searching for exoplanets and monitoring the sky for powerful stellar explosions,” Associate Professor Cole said.
Image: Members of the University of Tasmania physics department inspect the new, lightweight 1.27-metre mirror shortly after installation in the Harlingten telescope at Greenhill Observatory.