The Large Binocular Telescope

The Large Binocular Telescope (LBT) Project is a collaboration between institutions in Arizona, Germany, Italy, Indiana, Minnesota, Ohio and Virginia. The telescope on Mt. Graham in southeastern Arizona uses two 8.4-meter diameter primary mirrors mounted side-by-side to produce a collecting area equivalent to an 11.8-meter circular aperture. A unique feature of LBT is that the light from the two primary mirrors can be combined to produce phased array imaging of an extended field. This coherent imaging along with adaptive optics gives the telescope the diffraction-limited resolution of a 22.65-meter telescope. The first primary mirror was aluminized in April 2005. First light with a single primary mirror and a prime focus imager was achieved in October 2005. We describe here some of the technical challenges met and solved on the way to First Light. The second of two 8.4-meter borosilicate honeycomb primary mirrors has been installed in the telescope in October 2005 and was aluminized in January 2006. Binocular operation with two prime focus cameras is planned for Fall 2006. The telescope uses two F/15 adaptive secondaries to correct atmospheric turbulence. The first of these adaptive mirrors is now being integrated with its electro-mechanics.