Archive for Sloan Digital Sky Survey SDSS

Celebrating the Sloan Telescope

Posted in The Universe and Stuff with tags , , , , , , , , on May 9, 2018 by telescoper

A little bird tweeted at me this morning that today is the 20th anniversary of first light through the Sloan Telescope (funded by the Alfred P. Sloan Foundation) which has, for the past two decades, been surveying as much of the sky as it can from its location in New Mexico (about 25% altogether): the Sloan Digital Sky Survey is now on its 14th data release.

Here’s a picture of the telescope:

For those of you who want the optical details, the Sloan Telescope is a 2.5-m f/5 modified Ritchey-Chrétien altitude-azimuth telescope located at Apache Point Observatory, in south east New Mexico (Latitude 32° 46′ 49.30″ N, Longitude 105° 49′ 13.50″ W, Elevation 2788m). A 1.08 m secondary mirror and two corrector lenses result in a 3° distortion-free field of view. The telescope is described in detail in a paper by Gunn et al. (2006).

A 2.5m telescope of modest size by the standards of modern astronomical research, but the real assets of the Sloan telescope is a giant mosaic camera, highly efficient instruments and a big investment in the software required to generate and curate the huge data sets it creates. A key feature of SDSS is that its data sets are publicly available and, as such, they have been used in countless studies by a huge fraction of the astronomical community.

The Sloan Digital Sky Survey’s original `legacy’ survey was basically a huge spectroscopic redshift survey, mapping the positions of galaxies and quasars in three dimensions to reveal the `cosmic web’ in unprecedented detail:

As it has been updated and modernised, the Sloan Telescope has been involved in a range of other surveys aimed at uncovering different aspects of the universe around us, including several programmes still ongoing.


SDSS-III and the Cosmic Web

Posted in The Universe and Stuff with tags , , , , , on January 12, 2011 by telescoper

It’s typical, isn’t it? You wait weeks for an interesting astronomical result to blog about and then two come along together…

Another international conference I’m not at is the 217th Meeting of the American Astronomical Society in the fine city of Seattle, which yesterday saw the release of some wonderful things produced by SDSS-III, the third incarnation of the Sloan Digital Sky Survey. There’s a nice article about it in the Guardian, followed by the usual bizarre selection of comments from the public.

I particularly liked the following picture of the cosmic web of galaxies, clusters and filaments that pervades the Universe on scales of hundreds of millions of lightyears, although it looks to me like a poor quality imitation of a Jackson Pollock action painting:

The above image contains about 500 million galaxies, which represents an enormous advance in the quest to map the local structure of the Universe in as much detail as possible. It will also improve still further the precision with which cosmologists can analyse the statistical properties of the pattern of galaxy clustering.

The above represents only a part (about one third) of the overall survey; the following graphic shows how much of the sky has been mapped. It also represents only the imaging data, not the spectroscopic information and other information which is needed to analyse the galaxy distribution in full detail.

There’s also a short video zooming out from one galaxy to the whole Shebang.

The universe is a big place.