Location Matters Things to consider: Dark Sky, Good Seeing, High Altitude, Non-turbulent airflow and located Near the Equator: 1) Hawaii 2) SW United States 3) Northern Chile 4) Canary Islands, Esp. 5) South Africa 6) Southern Australia

Size Matters Astronomers want the largest primary mirror possible to increase light gathering power and maximize resolving power. One of the largest, older telescopes is the 5-meter (200-in) Hale Telescope on Mount Palomar, CA. A massive structure is needed to support its 14.5 ton primary.

New Ideas and Technology In the 1970s, the U. of Arizona built the Multiple Mirror Telescope, (MMT): 6, 1.8-m telescopes to produce the effect of a 4.5-m telescope. The MMT used an alt-az mount (the entire building moves to the proper azimuth). This idea of segmented mirrors is now used by Caltech in the 10-m Keck Telescopes and Texas for the 9.2-m Hobby-Eberly Telescope.

Spinning Ovens & Honey-Comb Mirrors (UofA Mirror Lab)
Large, chalk honeycomb-shaped pieces are arranged within an oven, which represent a large fraction of the volume. They add large chunks of high quality glass, slowly heating it. As the glass melts in the flat oven, they spin it (~7 RPM). As it cools, a concave surface forms. Once it's cooled (takes about 1-2 years) less glass must be removed for the final polish. When the polished surface is completed, the underlying chalk structure is removed using a high-pressure water hose.