Griffith Park Observatory Renewed

kw: travel notes, sightseeing

When I lived in Southern California I went to the Griffith Park Observatory several times a year to see a planetarium show, and usually to look through their telescope. Late on the second day of our trip (Saturday, May 16), I took my wife there. My brother had returned to his conference on Mayan studies, and his daughter took our son (her cousin) to hang out with her friends.

The park was so full we had to park a half mile from the observatory and walk up. I shot this picture from a spot near where we parked. The small dome on the left (east) houses the "nighttime" telescope, the large central dome is the planetarium, and the small dome at the west end (in front of the main dome from this perspective) houses the solar telescope and spectrograph used in the exhibits at the west end of the building. You can see in the picture that the western dome is open and facing the Sun. The building faces north.

The basement of the building, which used to be inaccessible to the public, houses two new attractions, the Gottlieb Transit, shown in part here, and the Nimoy Theater, which was not running any shows when we visited. We were short of time, so we didn't see any planetarium shows either. We just scoped out the museum and scientific displays on the main floor and the new Gottlieb exhibits.

The planet models seen here are Jupiter, Saturn and Neptune; Uranus is behind Saturn's ring and the smaller planets are off-view to the left. There is an exhibit below each, giving a succinct list of facts about each planet. The dark globe at lower right gives viewers some idea of (moderately) deep space. Seen from a particular angle, one sees the Big Dipper. You can barely see a distorted dipper shape from this angle. The seven bright stars in the Dipper are at quite different distances, so looking at the constellation from different angles you see it as aliens might see it from other parts of space.

This is a replica of one of Galileo's telescopes. It is about a meter long. I was surprised at how small the objective lens is, only about 2 cm (3/4 inch). My first telescope, made at age 11, has a diameter of 7.6 cm (3"). However, this was sufficient for Galileo to discover craters on the moon and the larger satellites of Jupiter.

This is part of a planetary and science history in the east wing of the main building. They also have the "donut hole" from the Palomar telescope's mirror. The entire mirror was polished to perfection, then the central meter was cut out for light to get to the prime focus and other instruments.

Until a few years ago, the "donut hole" was used as an indoor telescope (with a 55 foot focus!) that people could use to look at a small picture of Saturn in the other end of the building. Now it is on display against a wall, and its optical path is blocked by a scale model of the Palomar observatory.

A great uncle of mine was working at CalTech in the 1940s, and was one of the polishers of the big mirror. He and two dozen other men, chosen because their hand temperatures were the same, polished the mirror by hand. In the 1970s I worked in CalTech's Physics machine shop, and did some work that was carried out in the same room where that mirror was ground and polished. I was also working on a telescope, but this one was a radio telescope, made of lots of metal tubes that had to be very exact lengths. It was my boss's job to get the lengths right and mine to fit them together and attach the panels that made the reflecting surface.

The telescope we can look through, opened after dusk most evenings, is larger than most amateur instruments, but not considered all that large. It is 12.5 inches in diameter (32 cm), but is a refractor, using lenses instead of the mirror optics that most amateurs use. It is of superb quality, sixteen feet long, with its main focus f/15 to reduce secondary "rainbow" from its achromatic objective lens. I love looking through it. The beauty of a refracting telescope is that the objective has no obstructions, so images are perfectly clear without spikes or other artifacts. A reflecting telescope's mirror nearly always has a second mirror in front of it, to take the image out to where you can look at it. Light scattering off this "central obstruction" degrades the image a little.

I regret that we only had about 90 minutes to spend at the Observatory. We had a family dinner to get to, and congratulations to confer on our niece, in preparation for her graduation the next day.