The Big Bear Solar Observatory exploits the exellent climatic
conditions of Big Bear Lake to study the Sun, source of life
on Earth.  The observatory is located in the middle of Big Bear
Lake to reduce the image distortion which usually occurs when
the Sun heats the ground, producing convection in the air just
above the ground.  Turbulent motions in the air near the
observatory are also reduced by the smooth flow of the
wind across the lake, instead of the turbulent flow one would
have over mountain peaks and forests.  These conditions,
combined with the cloudless skies of southern California
and the clarity of the air at 2000 meters (6750 feet) elevation,
make the observatory a premier site for solar observations.
Since it was built in 1969, the observatory has produced many
of the finest observations ever obtained of the Sun.
Particularly well-known are the observations of solar activity
and flares which require the long sunlit days characteristic
of Big Bear.  The observatory is operated by the Center for
Solar Research at the New Jersey
Institute of Technology with support from the National
Science Foundation, NASA, and other agencies.

...

The telescopes are specially designed for solar observations.
The top floor of the observatory contains a telescope mount
with three main telescopes: a 65 cm (26 inch) reflector,
a 25 cm (10 inch) refractor, and a 15 cm (6 inch) refractor.
The smallest telescope monitors the whole Sun; the two larger
telescopes observe small regions of the Sun's surface at high
magnification.  Both of the larger telescopes are vacuum systems
to avoid air turbulence inside the telescope tubes.  The
special white paint used all over the observatory
diffusely reflects sunlight to reduce solar heating.
A large fan evacuates air from the dome so that the interior
of the dome remains at the same temperature as the outside air.
All of these features reduce distortion of the solar images
caused by small temperature differences in the air.  Each
telescope is independenly pointed at the Sun by a photoelectric
servo-guider, allowing each telescope to look at different regions
of the Sun.

The telescope is equipped with special filters which isolate
small portions of the visible spectrum which are absorbed and
emitted by particular elements at specific temperatures and
pressures, which allow different parts of the solar atmosphere
to be observed.  Most often, light from hydrogen, helium, and
calcium is used.  The observatory also has a spectrograph,
fed by the 65 cm telescope, which allows for more detailed
analysis of the light.  The images are recorded with digital electronic
cameras using several different computer systems.  The computers
controlling the cameras, as well as those controlling the
telescopes themselves, are operated from a control room on
the second floor of the observatory.  This keeps even the
small additional heat generated by the observers themselves
out of the dome.

Also on the second floor of the observatory is a "nose" jutting
out of the south side.  Inside the "nose" is a special telescope
which monitors the brightness of the Sun.  Small differences in
brightness between different parts of the solar surface can give
information on the nature of the solar cycle which cannot be
obtained otherwise.

On the causeway leading to the observatory building are two additional
telescopes which measure the oscillations of the Sun.  The study of
the oscillations of the surface of the Sun, helioseismology, allows
us to obtain information about the otherwise invisible solar interior
just as ordinary seismology (the study of earthquakes) allows geologists
to obtain information about the interior of the Earth.  The telescope
closest to the shore is part of the GONG (Global Oscillation Network
Group) project of the National Solar Observatory, while the small
telescope next to the observatory building is operated by the
Taiwan Oscillation Network.  Both of these telescope are parts
of networks of telescopes around the world, allowing continuous
observation of the solar oscillations.