Yerkes Observatory
| Yerkes Observatory | |
|---|---|
 Yerkes Observatory from the Air (2006) |
|
| founding | 1897 |
| IAU code | 754 |
| Type | Observatory |
| Coordinates | 42 ° 34 '13 " N , 88 ° 33' 22.5" W |
| place | Williams Bay |
| operator | University of Chicago |
| Website | University of Chicago - Astronomy and Astrophysics |
The Yerkes Observatory is a historic astronomy research facility in the United States , inaugurated in 1897 . It is located near Chicago on Lake Geneva in the state of Wisconsin , but is no longer in use today due to increasing air and light pollution .
The observatory was financed by Charles Tyson Yerkes , a US industrialist, after whom it was named. The main dome houses the largest lens telescope in the world to date with a 102 cm lens and 19.7 meters focal length.
Idea, financing and construction
In 1891, William Rainey Harper , then head of the University of Chicago , offered the astronomer George Ellery Hale a professorship . Hale agreed on the condition that the university build a completely new observatory .
Hale had learned that two 40 inch (102 cm) diameter glass optical lenses were being processed. His idea was to build a telescope with such a huge lens system.
In 1892 Harper and Hale visited the industrialist Charles Tyson Yerkes . Yerkes wanted to polish up his image and hoped to improve his reputation through sponsorship activities.
Harper and Hale appealed to Yerkes' ego - the intended telescope would, after all, be the largest in the world. In doing so, however, they concealed the high overall costs of the project. Yerkes agreed to finance the telescope. Harper and Hale tacitly assumed that he would also pay for the construction of the entire building. When Yerkes finally found out about it, he initially wanted to withdraw - there was never any talk of building a complete observatory. In contrast, Hale launched a press campaign in which he celebrated Yerkes as a generous sponsor and benefactor. He did not want to back down in public and secured the financing.
Yerkes continued to suspect he was being financially defrauded, especially since Hale had three additional spectroscopes purchased without informing him beforehand. In 1894 the foundations and mounting of the telescope were completed. At this point, Yerkes refused to put any further funding into the project. In the period that followed, the relationship remained tense. Nevertheless, in 1897, during the final phase, Hale managed to elicit additional funds from Yerkes. Completion was delayed as the main dome collapsed due to a design flaw. Yerkes saw it as the work of his political opponents, albeit without justification.
On October 21, 1897, the Yerkes Observatory was officially inaugurated. Yerkes gave a speech in which he indicated that astronomy was not for commercial purposes. The reward of their followers lies solely in their work and the results achieved. The speech earned him great applause.
Yerkes' generosity, however, only temporarily affected public opinion. In fact, he was denied social recognition in the USA until his death.
The great refractor
The telescope with an opening width of 102 cm and a focal length of 19.7 m was built under the guidance of telescope maker George Willis Ritchey . After completion, Ritchey made numerous improvements and optimized astrophotography .
The Yerkes refractor is still the largest lens telescope today . It represented the end of the history of the giant telescope , because the insurmountable technical limits were reached:
- Such large telescope lenses suffer from noticeable lens deflection due to their high weight .
- As glass lenses become thicker , more and more light is absorbed by them .
- The overall length of the telescope requires a correspondingly stable mechanical construction, whereby the mount must also be very delicate in order to keep the tracking errors far below 1 " with long exposures .
Because of these problems, the construction of large instruments went over to mirror telescopes , whose light-collecting opening reached 2.5 meters as early as 1917 with the Mount Wilson observatory .
The optics
The 40-inch lens consists of two lenses with different glasses. It is a doublet of crown glass and flint glass spaced 8 3/8 inches apart . The crown glass converging lens weighs 200 pounds and is 2.5 inches thick at the center and 3/4 inch at the edge. The concave flint glass is 1.5 inches thick in the center and 2 inches thick on the edge. It weighs over 300 pounds. Taken together, the glass of the lenses has a weight of around 230 kg.
In 1900 Hartmann published in Astrophysical Journal 12/46 a method for assessing the quality of such a large telescope lens. Shortly afterwards he wrote a letter to Hale to test the quality of the Yerkes lens. On February 1, 1902, Barnard made the corresponding photographic plates for this. In April of the same year, Hartmann reported his results to Hale. Ichinohe (?) Also carried out measurements in 1906, which led to a result similar to that of Hartmann. After discussing the measurement results, he decided: "As far as you can see from these few points, the objective is very excellent." However, he restricted the result insofar as not all the required measurement ranges were covered. Hartmann then suggested a more intensive examination.
Other research
In addition to the large refractor, there is a reflector with a 61 cm main mirror and several smaller telescopes for training purposes in Yerkes.
Research is currently being carried out in the field of interstellar matter , the structure of globular clusters and near-earth asteroids (NEA), which are classified as near-earth objects (NEO). In addition, it operates a research center for the production and improvement of scientific instruments.
In March 2005, the University of Chicago announced that it intended to sell the observatory and the surrounding land. In 2007, after protests from various quarters, the company temporarily refrained from selling. Since then, the observatory has mainly been used for educational purposes and for public relations. On March 7, 2018, the University of Chicago announced that it would finally cease operations of the observatory by October 1, 2018. While the university is concentrating its astronomical research activities on large telescopes in Chile, the training and public relations work will in future be carried out by the Hyde Park Campus.
The asteroid (990) Yerkes is named after the observatory.
See also
Individual evidence
- ↑ GE Hale in: The Astrophysical Journal vol. 6, 1897, p. 43.
- ↑ Philip Fox in: Astrophysical Journal vol. May 27, 1908, p. 4 f.
- ^ Final Report of the Yerkes Study Group. (PDF; 416 kB) November 30, 2007, accessed on August 16, 2012 (English).
- ↑ UChicago activities at Yerkes Observatory to end in 2018. March 7, 2018, accessed March 14, 2018 .
- ^ Dictionary of Minor Planet Names, Volume 1 in the Google Book Search
