The Large Binocular Telescope

Abstract

The Large Binocular Telescope (LBT) Observatory 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 borosilicate honeycomb 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 on-sky phasing of the two telescopes in the mid-infrared occurred in October 2010 with the LBTI instrument in Fizeau mode. The telescope control system has been upgraded to allow binocular (2-sided) observations with pairs of instruments. The prime focus cameras (LBC) routinely operate in this mode. Improved collimation and pointing models have been deployed to keep both sides collimated and pointed at the same target. The control system has also been upgraded to allow observations of solar system objects at non-sidereal tracking rates. Science observations are scheduled for 60% of the nights including a significant fraction of adaptive optics imaging with the first adaptive secondary mirror and the FLAO system with natural guide stars. MODS1, a nearUV-optical spectrometer, has been added to the suite of science instruments along with LBC (visible imagers) and LUCI1 (near infrared spectrometer). LMIRcam (2-5 microns) and PISCES (1-2.5 microns) have been used for adaptive optics imaging. The remaining nights are scheduled for telescope and instrument commissioning activities as new instruments arrive. The second of the two F/15 adaptive secondary mirrors has been installed on the telescope in Fall 2011 and has been commissioned on-sky in Spring 2012.