Description - Information courtesy of The University of Arizona
Mount Graham was selected from a survey of 280 potential mountain sites on the basis of astronomical considerations such as clear skies, low light pollution, low atmospheric water vapor, and ease of access and support. Mount Graham is in the Sonoran desert climatic zone along with established sites such as Kitt Peak, Mount Hopkins and Mount Lemmon; its intrinsic climatic properties are those which have made the desert southwest so productive for astronomy for almost a century. Mount Graham does, however, have the additional advantages of greater altitude and very low light pollution. Unlike rival sites outside the continental United States, it has excellent logistics: sufficient area for several telescopes, a pre-existing paved highway, good connections by air and road, and a high level of local technical support.
The only astronomical site characteristic not considered in the initial survey was image sharpness (astronomical seeing) since there is no generally accepted method of doing this other than by making in situ measurements. The image sharpness on Mt. Graham has, therefore, been the subject of a ten year study carried out by Dr. Richard Cromwell, Dr. Nick Woolf, and others. These studies first identified the Emerald Peak region as the best general area on Mount Graham for an observatory, because it provides good image sharpness and space for telescopes. In the second study phase, measurements were made of seeing differences between various locations within the 150-acre Mt. Graham scientific research area.
- All of the telescope sites which Steward Observatory has tested extensively within the 150-acre Mt. Graham Astrophysical Research Area, around Emerald Peak, provide excellent astronomical seeing. Several years of data show that the typical image size for a large telescope located 25 meters above the ground is about 0.6 arcseconds; this compares favorably with the image quality at the Multiple Mirror Telescope on Mount Hopkins in Southern Arizona. The table below shows that the Emerald Peak sites are also competitive on a worldwide basis (other data provided by the observatories concerned).
Recreation - Educational.
Climate - Cold air masses from Canada sometimes penetrate into the state, bringing temperatures well below zero in the high plateau and mountainous regions of central and northern Arizona. The lowest readings can dip to 35 degrees F below zero. High temperatures are common throughout the summer months at the lower elevations. Temperatures over 125 degrees F have been observed in the desert area. Great extremes occur between day and night temperatures throughout Arizona. The daily range between maximum and minimum temperatures sometimes runs as much as 50 to 60 degrees F during the drier portions of the year. During winter months, daytime temperatures may average 70 degrees F, with night temperatures often falling to freezing of slightly below in the lower desert valleys. In the summer the pine-clad forests in the central part of the state may have afternoon temperatures of 80 degrees F, while night temperatures drop to 35 or 40 degrees F.
Mt. Graham Observatory is located in The Pinaleño Mountains .The Pinaleño Mountains are a remote mountain range in southeastern Arizona. They have over 7,000 feet of vertical relief, more than any other range in the state. The mountains are surrounded by the Sonoran-Chihuahuan Desert.