Optical telescopes and enclosures for ground-based interferometry: the CHARA array

The telescope requirements of optical interferometry are somewhat different from conventional astronomy. The need for multiple units (in the CHARA case initially five, eventually seven) accentuates the importance of cost control, and at the same time provides opportunity for cost savings by careful procurement and production practices. Modern ideas about telescope enclosures offer significantly reduced dome seeing, but it is difficult to capture these benefits at low cost. The CHARA group has followed a series of design and bid procedures intended to optimize the cost-performance of the telescope+enclosures. These have led to a compact but massive telescope design, blending modern and classical features, an unusual mirror blank selection process (directly competing several mirror blank technologies), and a novel telescope enclosure concept which allows a continuous trade between wind protection and natural ventilation. This contribution will review anti motivate the design decisions and show the resulting equipment and facilities.