The Australian Astronomical Observatory (AAO) have posted
photo galleries on their Facebook page which show the process of
cleaning and re-aluminising the 3.9m mirror.
The observatory has its own vacuum chamber in a floor below the
telescope and the mirror is removed and lowered down to that
floor whenever it needs re-aluminizing, typically on an annual basis.
See that process here -
https://www.facebook.com/AustralianA...type=3&theater
The mirror weighs 16.19 tonnes and is fabricated from
Cer-Vit glass.
The diameter of the central hole is 1.067m.
In one image you will see a close-up of the 2.5g coil of aluminium
which is vaporized in the vacuum chamber and provides the mirror surface.
Cleaning and coating gallery here -
https://www.facebook.com/AustralianA...type=3&theater
AAO post photo gallery of cleaning and re-aluminizing the 3.9m AAT mirror
