The Big Bear Solar Observatory is located on the northern side of Big Bare lake in California. Established in 1969, the observatory is located out in the open waters of the lake to help improve the seeing. It is one of a network of observatories around the world that provide 24 hour monitoring of solar activity. Others include the Culgoora Solar Observatory and the Learmonth Solar Observatory.
While origionally access to the observatory was only via boat, these days it is via a causeway, about 150m long.
Information display by the enterance to the causeway. Normally the causeway enterence is locked and access to prohibited. However on the day that I was there it was open and while I was there one of the astronomers working at the telescope arrived and after chatting with him for a while, he invited me in to have a look around.
There are 2 domes at the end of the causeway. The larger one houses the main telescope while the smaller one houses a 10 cm Full Disk H-alpha Patrol Telescope.
The patrol telescope dome.
The main telescope dome. On the day when I was there the telescope was not in use, mainly due to the extremely high winds and resulting very poor seeing.
The main telescope is a 1.6m off-axis Gregorian telescope, with the primary mirror being figured from a 1.7m blank by the University of Arizona Mirror Lab as a proof-of-concept for the mirrors of the Giant Magellan Telescope.