Yerkes Observatory

The Yerkes Observatory is an historic, 1897, inaugurated research center for astronomy in the United States. It is located near Chicago's Lake Geneva, Wisconsin, but is today due to the increasing air and light pollution little longer in use.

Was financed by Charles Tyson Yerkes Observatory, an American industrialist, after which it was named. The main dome houses the largest to date lens telescope in the world with a 102cm - lens focal length and 20 meters.

Idea, financing and construction

In 1891, William Rainey Harper offered, then director of the University of Chicago, the astronomer George Ellery Hale to a professorship. Hale agreed under the condition that the university had built a completely new observatory.

Hale had learned that two optical glass lenses (102 cm) were processed with a diameter of 40 inches. His idea was to build a telescope with such a huge lens system.

1892 investigated Harper and Charles Tyson Yerkes Hale industrialists on. Yerkes wanted to bolster his image and hoped for by sponsors activities ENHANCE a reputation.

Harper and Hale appealed to Yerkes ' ego - the planned telescope would eventually be the largest in the world. Here, however, they concealed the high total cost of the project. Yerkes agreed to fund the telescope. Harper and Hale went tacitly assumed that he would pay the construction of the entire building. As Yerkes finally found out, he wanted to retire first - from building a complete observatory had never been mentioned. In contrast, Hale launched a press campaign in which he was celebrating Yerkes as a generous sponsor and benefactor. This would now make the public not back out and secured funding to.

Yerkes had continued to be suspected of being cheated financially, especially since Hale was additionally acquire three special spectroscopes, without informing him beforehand. 1894, the foundations and the mount of the telescope had been completed. At this time, Yerkes refused to put more funds into the project. In the following years the relationship remained tense. Nevertheless, we succeeded Hale in 1897, during the final phase, Yerkes to elicit more money. The completion was delayed because the main dome collapsed due to a design flaw. Yerkes saw it, though untitled, the work of his political opponents.

On 21 October 1897, the Yerkes Observatory was officially opened. Yerkes gave a speech in which he pointed out that astronomy is not pursuing commercial objectives. The reward their followers lie exclusively in her work and the results achieved. The speech brought him wide acclaim.

Yerkes ' generous attitude influenced the public opinion but only temporarily. Indeed, the social recognition he was denied until his death in the USA.

The large refractor

The construction of the telescope with 102 cm Opening width and 19.7 m focal length was carried out under the guidance of the telescope maker George Willis Ritchey. Ritchey took after completion before numerous improvements and optimized astrophotography.

The Yerkes refractor is still the largest telescope. It turned in the history of giant telescopes a final point since you came to the insurmountable technical limitations:

• Such large telescope lenses experienced due to the sheer weight of a noticeable deflection;
• With increasing thickness of glass lenses more and more light is absorbed by them;
• The overall length of the telescope requires a correspondingly stable mechanical construction, the mount must be very finely continuous.

Because of these problems, it went in the subsequent period through the construction of major instruments for reflecting telescopes, the light -collecting opening in 1917 with the Mount Wilson Observatory reached 2.5 meters.

The optics

The 40-inch lens consists of two lenses with different glasses. There is a doublet of crown glass and flint glass, with a spacing of 8 3 /8 inch. The crown glass weighs 200 pounds and has in the center a thickness of 2.5 inches and on edge 3 /4 inch. The flint glass has a thickness of 1.5 inches and 2 inches at the edge in the center. It weighs about 300 pounds. Taken together, the glass of the lenses, thus has a weight of about 230 kg.

Hartmann published in 1900 in the Astrophysical Journal 12/46, a method for assessing the quality of such a large telescope objective. Shortly afterwards, he offered in a letter to Hale, to check the quality of the Yerkes lens. On February 1, 1902 Barnard made ​​this to the appropriate photographic plates. In April of the same year Hartmann reported its results to Hale. Ichinohe (? ) Conducted in 1906 also measurements that led to a similar result as that of Hartmann. This was after the discussion of the results: "So much can be seen from these few points, the object-glass is quite excellent. " However, he restricted the result is a sense that not all required measuring ranges were covered. Hartmann then proposed a more intensive examination.

Other research

In addition to the large refractor are in a Yerkes reflector with 61 cm primary mirror and several smaller telescopes for training purposes.

Currently you researching in the field of interstellar matter, the structure of globular clusters and near-Earth asteroid (NEA ), which are among the near-Earth objects ( NEOs). Moreover, it operates a research center for the production and improvement of scientific instruments.

In March 2005, the University of Chicago reported that one intends the observatory and the surrounding land for sale. In 2007, one distance has after protests from various quarters but again taken from a sale. In the future, less research is conducted at the observatory to make more use for educational purposes.