SSO Update

Published in the RSAA Lunations
Vol1 Issue27 1–30 April 2022

The class of 2022

Every year, around March or April, we recoat the primary mirror of the AAT. This is a big job, taking several weeks of careful planning. It requires the 16 tonne mirror to be removed from the telescope, the old coat of aluminium removed, the new one put on, and the mirror put back. It takes about four days for the whole process, and during that time the telescope is unavailable.

A fresh coat of aluminium has a reflectivity of about 90% at a wavelength of 500 nm, dipping down to 86% at 850 nm and jumping up to 97% beyond 2000 nm. At wavelengths longer than 500 nm, silver and gold have higher reflectivity. It is not uncommon to see mirrors coated with either silver or gold (e.g. the Gemini primary mirror uses silver and the James Webb Space Telescope mirrors use gold).

Farewells

As noted in the last edition of Lunations,  Kristin Fiegert and John Goodyear will retire at the end of June. We will be having a farewell party for Kristin and John at Pilliga Pottery on May 14. Please contact Murray Riding (Murray.Riding@anu.edu.au) if you wish to join the farewell. Chris McCowage will also retire at that time. Combined, Kristin, Chris, and John  have worked 75 years at SSO. We will miss them.

Harry Abbot and Daniel Bonello will also be leaving SSO this year. While they have not worked as long 75 years, they have contributed enormously to observatory, and we will miss them too.

 

Chris Lidman on behalf of SSO

_{Picture: The class of 2022, appropriately masked, in front a freshly coated mirror}