A new pair of lenses for the Mayall

[Ptah]

http://www.symmetrymagazine.org/article/a-new-pair-of-lenses-for-the-mayall

The delicate process of lens crafting takes time and care. For your typical prescription eyeglasses, expect two weeks for proper sizing and glare-resistant coating. For a four-meter telescope with meter-wide lenses, a similar procedure takes well over a year.

The Dark Energy Spectroscopic Instrument project is the latest in a line of sky surveys to obtain custom lenses for an existing telescope. DESI arranged for refurbishments to the Mayall Telescope at the Kitt Peak National Observatory in Arizona, where it will create a three-dimensional map of a third of the sky in a quest to measure dark energy.

“DESI’s ultimate goal is to precisely measure and map the expansion rate of the universe and when it started to accelerate in its expansion,” says Michael Levi, the DESI project director and a physicist at the Department of Energy’s Lawrence Berkeley National Laboratory. “We’re looking back in time about 11 billion years, and we can do this with the help of a new corrector and high-precision lenses.”

The upgrade includes six new lenses, the two heaviest of which are ready for a final coating before integration into the brand new corrector barrel. Those nearly complete lenses, Corrector Lens 1 and Corrector Lens 4 (C1 and C4), have been in production since early 2015. Their journey began as a raw chunk of glass.