Barry,
Les, If my memory is correct Big Bear Observatory is a solar observatory. What makes the location important to that type of observing?
Solar Observatories have to contend with (surprize, surprize) solar radiation. Large lakes have the effect of calming the air above them, particularly when they are far above the surrounding heated valleys. Some of the very finest photographs of Mercury taken from Earth (prior to several spacecraft orbiting the planet) were taken at near Noon. Mercury is as high as it gets and the air has had time to even out.
Some solar Observatories like McMath in Kitt Peak give up any hope ofdoing anything besides viewing the Sun. These places try to create the largest image possible at prime focus. In most such Observatories, you must wear reflective suits to avoid dangerous sun burns if you happen to get hit by reflected light. McMath is big enough to avoid this problem. You have a minute or two to get out of the beam before getting a nasty burn.
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