TelescopesGriffith Observatory is one of the premier public observatories in the world. One of the principal reasons is the presence and regular availability of high-quality public telescopes. Griffith J. Griffith wanted the public to have the opportunity to look through a telescope, which he felt might broaden human perspective. Mounted in the copper-clad domes on either end of the building, the Zeiss and solar telescopes are free to the public every day and night the sky is clear.
Since opening in 1935, more than seven million people have put an eye to Griffith Observatory's original 12-inch Zeiss refracting telescope. More people have looked though it than any other telescope in the world. Located in the roof-top dome on the building's east end, the Zeiss telescope is intended mainly for nighttime viewing by the general public, commonly targeting the Moon, planets, and brightest showpiece objects of our galaxy. A popular public destination when special celestial events occur, more people viewed Halley's Comet and comets Hale-Bopp and Hyakutake through the Observatory's Zeiss telescope than any other telescope on the planet.
A 9½-inch refracting telescope, also by Zeiss, was added piggyback to the 12-inch in 1955. It aided with research work and is also used for public observation.
Griffith Observatory's three solar telescopes bring the Sun directly to visitors in the west rotunda of the Ahmanson Hall of the Sky. On clear days, each of these telescopes provides a different real-time view of our local star, including sunspots and solar flares. The three beams of sunlight for the telescopes are focused into the rotunda by a triple-mirrored tracking device called a coelostat (Greek for 'sky-stopper'), which is located above in the western dome of the building. The solar telescopes operate only during clear daytime hours.
A coelostat is one option used in solar observatories when moving a small tracking mirror is preferable to moving a large telescope attached to heavy equipment. Designed by Russell W. Porter, famed for his intricate cut away illustrations of the workings of the 200-inch Hale Telescope, Griffith Observatory’s coelostat solves the problem of feeding three different telescopes with sunlight, while delivering their images to three fixed displays in the west rotunda of the museum. The incoming light bounces off from one of three tracking mirrors, and is bounced up to one of three mirrors that are each aimed into three different instruments. The center beam passes through a telescope and a projecting lens, to another mirror, and displays the sun and its spots as a 21-inch wide image on a ground glass screen. The northern beam bounces into a spectroscope located in a pit beneath the museum floor, and back up to an eyepiece, through which a detailed view of the sun’s spectrum is visible. The southern beam reflects into a kind of telescope called a hydrogen-alpha filter. By looking through an eyepiece, the visitor will see that all but one specific shade of red has been filtered out. The sun’s energy is harmless at that wavelength, and the fluorescent hydrogen visible through it makes the turbulent plasma of the sun’s outer layer, the chromosphere, dramatically visible.
The coelostat instrumentation in the dome and three telescopes housed in the rotunda remain essentially unchanged by the renovation and expansion project, other than new motors for the dome, new electrical service, and restoration of the telescope bronze and optics. A new station in the gallery receives live signals from each of the telescopes to provide an equivalent observing experience for those unable to climb the stairs to the rotunda where the telescopes are mounted.
On any given night, Observatory staff may set up one or more free-standing telescopes on the lawn or East Observation Terrace to enable more people to put their eyeball to the sky. Once a month, the Los Angeles Astronomical Society and Sidewalk Astronomers hold a star party at the Observatory in which many more telescopes are available for public viewing.
In addition, the Observatory has mounted a number of coin-operated telescopes along the south and west perimeters of the building. These devices enable visitors to look at objects in the Los Angeles Basin and surrounding mountains.