-Outside Diameter: 8.10meters/26.58feet

-Central Cassegrain Hole: 1.18meters/3.87feet

-Thickness: 20cm/7.87inches

-Optical Configuration: Ritchey-Chretien Cassegrain

-Optical Surface: Concave, hyperboloid

-Surface Accuracy: 15.6 nm RMS* (assumes perfect active mirror support)

-Mirror Polished By: REOSC, St. Pierre du Perray, France

-Measured Focal Length w/o Secondary: 14.402 meters/47.25feet

-Effective Focal Length with Secondary: 128.120 meters/420.341feet

-Mass/Weight of Finished Mirror: 22.22 Metric Tonnes/24.5 US Tons

-Material: Corning ULEä (Ultra Low Expansion) glass manufactured at Corning

Incorporated, Canton, New York

*RMS = Root Mean Square – An analysis method for characterizing/describing

the surface accuracy of an optical surface that relates directly to the final

image quality.