Overwhelmingly Large Telescope

Overwhelmingly Large Telescope (OWL ) was the working title of a telescopic study of the European Southern Observatory ( ESO). Since there is already a Very Large Telescope (English for Very Large Telescope, shortly VLT) and similar terms such as " Extremely Large Telescope" ( Extremely Large Telescope), called the new project a little self-deprecating Overwhelmingly Large Telescope ( Overwhelmingly Large Telescope). At the same time, the name alludes to the good night vision capabilities of the owl (English owl ). The OWL - study with 100 m primary mirror diameter is no longer being pursued by ESO since the end of 2005, instead it goes for a European Extremely Large Telescope with 39 m diameter mirror.

Proportions

This ground-based optical telescope had a primary mirror diameter of 100 m, which is about a hundred times the surface area and thus the hundred times the light gathering power of the then largest telescope mirror ( Keck telescopes, Mauna Kea ). The surface of the primary mirror would be larger than the area of all the currently in-use professional telescopes together. Even the secondary mirror would be overwhelming in size with 30 m diameter. Both mirrors were not made ​​of one piece (which is not technically feasible, and because of the extremely high weight would also make sense ), but from hundreds of mirror segments composed. The primary mirror is nevertheless still consist of 3048 individual hexagonal segments, the secondary mirror of 216 segments. All segments of the main mirror to in order to save costs, have the same curvature and together form a spherical surface, rather than the usual parabolic or hyperbolic shape.

So even resolutions of only 0.001 arcseconds will be possible. With an OWL could be stars up to 38th magnitude ( mag) observed. With the Hubble Space Telescope in 2004, an observation to 31 is may be possible - that is, one could observe with OWL still about 625 times fainter objects than Hubble, or 625 trillion times fainter than the naked eye under optimal viewing conditions.

Construction

Unlike existing large telescopes should OWL not be mounted under a dome, but are themselves freely and be protected during the day or in bad weather by an approximately 220 m wide, self-supporting hall. This would be run for the observations to the side.

An important problem would be to keep the weight by using new materials and designs as small as possible, because the telescope must be moved with utmost precision yes. The investigations were based on a total of 15,000 tons total weight. For 300 bogies should be used with friction drive, running on circular tracks.

The angedachte optical setup consisted of a spherical primary mirror, a secondary mirror and are planning a four element corrector catoptrical. The spherical primary mirror can be composed of uniform segments; the flat secondary mirror is relatively insensitive to changes in position that are difficult to avoid in the size of the telescope. The corrector compensates for the spherical aberration of the primary mirror and includes the adaptive optics system, which compensates for atmospheric interference of the incident light. The corrector would also compensate for the relatively strong deformation of the open construction by wind.

The total cost was estimated at about 1.2 billion euros.

Location

Different locations are for such a giant telescope in conversation, including the northern Chilean Atacama desert, where there already are a number of large telescopes such as the Very Large Telescope, or the Canary Islands, where in 2005 the Gran Telescopio Canarias was completed. Even over a site near or in Antarctica is thought intensified since the fall of 2004, after studies have shown that there south to 75 degrees width 3200 m, situated above the sea level plateau Dome C would be by far the cheapest place on earth for a telescope: very clean air, almost no stray light, little wind, drier climate than in the Sahara, thin air by the altitude. These conditions come to a location in space already quite close. With a telescope of this size, the aim is to achieve optimal observation conditions by as many criteria. Particularly suitable are therefore possible high-altitude sites in very dry areas with as low seismic activity. The proximity to the sea is favorable because there is less disruptive air turbulence occurs. In addition, the location should be as far away from major metropolitan areas to avoid interference from stray light. Therefore come, for example, Europe or the North American coast from the outset not considered because they are colonized much too dense. A somewhat lesser role now plays the accessibility that astronomers nowadays no longer have to always come in person for the observations. Highly qualified personnel on site who knows the intricate instruments exactly leads, more often from the observations according to the instructions of the applicant. The observation data is sent via the Internet or on disks.

View

A study of the OWL concept was completed and tested in the fall of 2005 by a commission of experts. While the validity of the concept has been recognized, the Commission recommended that the risks to cost and schedule instead a still very large telescope with a 39 m primary mirror diameter, which is now built from 2013 by ESO as a European Extremely Large Telescope. In this respect, a humorous explanation of the abbreviation proved true in OWL for " Originally what larger " (Originally it was bigger ) is.