In 2006 we decided to visit the Keck Observatory on the Big Island of Hawaii. The two 10 meter Keck telescopes are located on Mauna Kea at an elevation of 13,796 ft. and were the largest in the world at that time. The primary mirrors of each are composed of 36 hexagonal segments pieces that work together as a single piece of reflective glass. In 2008 the Gran Telescopio Canarias at 10.4 meters was completed, but the best seeing remains at Keck. This has much to do with its location high on top of an inactive volcano in the middle of the Pacific Ocean with stable air and little light pollution.
We planned for our visit by taking our warmest coats (not what most people carry on the plane to Hawaii) and renting a four-wheel drive vehicle. Only four-wheel drive vehicles are allowed on the road from the visitor center, which is at 9,200 ft., to the telescopes at the top. The tour purposely began at the visitor center with a 30 minute presentation to help us acclimate. Even then, we definitely felt the lack of oxygen at the summit.
We planned for our visit by taking our warmest coats (not what most people carry on the plane to Hawaii) and renting a four-wheel drive vehicle. Only four-wheel drive vehicles are allowed on the road from the visitor center, which is at 9,200 ft., to the telescopes at the top. The tour purposely began at the visitor center with a 30 minute presentation to help us acclimate. Even then, we definitely felt the lack of oxygen at the summit.