The Blanco 4-m Telescope Primary Mirror aluminization

    The Blanco 4-m telescope primary mirror, cleaned of its old coating of aluminum prior to installation in the vacuum chamber used to apply a new coating.   The 15-ton mirror is made of a glass called Cer-Vit, which has a very low coefficient of thermal expansion (and is no longer available).  On Wednesday 30th March, we applied a very high quality, 100nm thick layer of pure aluminum.  In this condition, the mirror is more reflective than it has been in over a decade and will provide a good start to the forthcoming Dark Energy Survey.