The Zeiss Telescopes
Griffith 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 dome on the east end of the building is the Zeiss telescope array. This telescope is free to the public every night the the Observatory is open and the sky is clear.
The 12-Inch Zeiss Refracting Telescope
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.
The telescope itself is in excellent condition and was unchanged by the renovation and expansion project. The copper roof of the telescope dome was repaired and restored, and the dome's drive mechanisms were replaced. The most significant change is the addition of a new exhibit station located in the Hall of the Eye exhibit hall below the telescope dome. The station provides live video and audio feeds from the telescope and allows visitors unable to climb the stairs into the telescope dome to have an observing experience. Most nights, other telescopes also are available on either the roof or front lawn to allow those in wheelchairs to observe directly.
When the night sky is clear, the Zeiss telescope is open from the roof and serves up to 600 visitors per night. One of the Observatory's experienced telescope demonstrators guides the public in looking through the eyepiece of the 12-inch Zeiss refractor (so called because its light is collected and focused by a 12-inch diameter glass lens at the front of the 16-foot-long telescope tube). The main telescope tube carries a smaller 9-inch refracting telescope piggyback, which permits two different views of a single object, as appropriate.
The telescope sits on a tilted mounting (an equatorial mount) aligned with the Earth's axis, and it is slowly turned by a motor to compensate for the Earth's rotation so that objects remain centered in view for as long as is desired. Counterweights precisely balance the telescope so that the Telescope Demonstrator can easily move the instrument by hand in spite of its 9,000-pound weight. The unique design of construction by Zeiss also counteracts the bending of the telescope due to gravity with counterweighted levers in the telescope's tube and mounting. Such a system is said to be "stress compensated."
The genesis of Griffith Observatory's public telescope occurred when Griffith J. Griffith was invited to visit to Mount Wilson Observatory, then home to the world's largest operating telescope, the 60-inch reflector. While there, he was given the opportunity to view a celestial wonder through the telescope. Profoundly moved by the experience, Griffith seized on the idea of constructing a public observatory with a telescope that could be used by all residents of Los Angeles. He specified in his will that the telescope was to be "at least 12-inches in diameter" and "complete in all its details" and was to be located "high and above the Hall of Science." In 1931, the Griffith Trust ordered the telescope from the Carl Zeiss Company of Jena, Germany; the $14,900 spent on the instrument was the first purchase of material for Griffith Observatory.
Manufacturer: Carl Zeiss/ Jena, Germany, 1931-34
Installation: Griffith Observatory. Los Angeles, 1935
Objective Diameter = 11.8-inch (300 mm)
Objective Focal Length = 198 inches (5.03m)
Objective Focal Ratio = F/16.7
Mounting Type: Zeiss offset-fork stress compensated equatorial.
Weight of moving parts: 4.5 tons
Astronomic Latitude 34 deg. 06 min. 46.8 sec.
Astronomic Longitude 118 deg. 18 min. 5.5 sec W
Elevation: 1172 feet (357m) (center of motion)
Manufacturer: Carl Zeiss/Jena Germany 1920s?
Installation: Originally mounted on automobile owned by Charles Stoody of Whittier California in 1933, and sold to Griffith Observatory in 1954. Piggy back mounted on 12-inch Zeiss in 1955.
Objective Diameter = 9½-inches (242 mm)
Objective Focal Length = 141 inches (3.58 m)
Objective Focal Ratio = F/14.8