Tuesday, June 28, 2005

Photos Of The "Big Eye" At Mt. Palomar Observatory.

The Mount Palomar Observatory (website here) had its first-ever open house on June 25, 2005. Although the observatory is open to the public every day, for the first time at the open house visitors were able to go inside the domes of two of the observatory's telescopes, including "The Big Eye," as they call the 200 inch scope. The photos that follow are the first in a series taken at the open house. Today's photos are of the 200 inch telescope. Unfortunately, the quality of these photos is probably the worst in the series. It was very dark inside the dome. (A suggestion for next year's open house. Turn up the lights.) Other photos this week will include two other telescopes and some shots of the compound and the open house. They will be much clearer. I promise. The first photo below is of Big Eye's dome.



The large telescope's dome is the dominant feature on the 200 acre observatory site. The dome is 135 feet tall by 137 feet in diameter and weighs 1,000 tons. From a distance the dome is obviously a large structure. But it's a close-up view that drives home the dome's enormous size. The picture below shows just how big the dome is. Note the tiny people walking along the catwalk that encircles the dome.



Big Eye's enormous size is revealed inside the dome where the scope has made its home since 1948. The scope is so large that a small cage-enclosed control room is attached to the bottom it. The control room hangs about 8 feet or so above the floor. The picture below is a shot of the bottom of the scope and the cage hanging above the floor.



Most telescopes give the impression of fragility. Not this one. Big Eye's 200 inch mirror alone weighs 40 tons. Its huge size requires massive machinery to move it about inside the dome and position it for viewing. The impression is not of a delicate instrument at all. Instead the scope's steel framework and machinery creates an impression of massive strength. Almost like a very large cannon. This next picture was taken from the floor and shows part of the mechanism that controls the scope's movement.



This next picture was taken from an inside second-story catwalk and shows more of the machinery that holds the scope and moves it around.



This picture is once again taken in near darkness. It's also taken from the second story catwalk. It shows the scaffolding that holds the telescope nestled in the machinery. You can click on the image to increase its size. With luck this may make it easier to view.



Back on the floor for a shot of the astronomers in the cage preparing for the night's viewing. There's up to a four-year waiting list for telescope time on Big Eye. Bad weather or technical difficulties can ruin an observation run. There's no do-overs, either. If the run is ruined the astronomers have to get back on the waiting list and hope that next time the weather is clear. The weather was good on this day so nobody in the control cage appeared particularly nervous. They were spending a lot of time huddled around the computers, however.



Like any machine the 200 inch telescope at Palomar needs maintenance. The mirror has to be cleaned and re-aluminized every two years or so. (Click here for website showing that process.) Besides the telescope and its machinery, there were two structures used in the aluminizing process. The first picture shows the unit that holds the mirror when it is removed from the scope for cleaning.



This next picture shows the re-aluminizing unit. During re-aluminization the 17.5 ton unit is lifted by a crane to the top of the unit holding the mirror. Air is evacuated and tungsten coils with aluminum draped on them are heated, which vaporizes the aluminum and coats the mirror leaving it shiny and new. The mirror just happened to have been re-aluminized the week before the open house.



Finally, the picture below shows a small replica of the 200 inch telescope. The replica is controlled by an electric motor that visitors can operate to learn how the scope moves. Unfortunately, this is probably the best photograph of what the scope looks like that I was able to take.



That's it for today's photographs. Come back again for others, including the 60 inch scope, the Palomar Testbed Interferometer, and more.

-tdr

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