TARGET 080917

The Sloan Digital Sky Survey

Starting shot
The Sloan telescope is about 100 miles from the nearest big city, El Paso, atop a paradise of soaring ponderosa pines and Douglas firs. It is located atop the mountain which overlooks Alamogorgo, New Mexico, and can be seen from most places in the city.

The Sacramento Mountains rise like brilliant green drapery of the New Mexican desert. Below, a desert expanse as large as Massachusetts stretches to the horizon. On one side is the White Sands Missile Range; on the other, the city of Alamogordo. At night, a deep blackness descends.

The Sloan Digital Sky Survey (SDSS) is one of the most ambitious and influential surveys in the history of astronomy. Over eight years of operations (SDSS-I, 2000-2005; SDSS-II, 2005-2008), it obtained deep, multi-color images covering more than a quarter of the sky and created 3-dimensional maps containing more than 930,000 galaxies and more than 120,000 quasars. SDSS data have been released to the scientific community and the general public in annual increments, with the final public data release from SDSS-II scheduled for October 31, 2008. SDSS-III, a program of four new surveys using SDSS facilities, began observations in July 2008, and will continue through 2014.

The SDSS used a dedicated 2.5-meter telescope at Apache Point Observatory, New Mexico, equipped with two powerful special-purpose instruments. The 120-megapixel camera imaged 1.5 square degrees of sky at a time, about eight times the area of the full moon. A pair of spectrographs fed by optical fibers measured spectra of (and hence distances to) more than 600 galaxies and quasars in a single observation. A custom-designed set of software pipelines kept pace with the enormous data flow from the telescope.

During its first phase of operations, 2000-2005, the SDSS imaged more than 8,000 square degrees of the sky in five optical bandpasses, and it obtained spectra of galaxies and quasars selected from 5,700 square degrees of that imaging. It also obtained repeated imaging (roughly 30 scans) of a 300 square degree stripe in the southern Galactic cap.


This is the bottom of the 2.5-meter survey telescope, where the instrument package(either mosaic camera or spectrograph) is mounted.


Looking inside the base of the 2.5-meter survey telescope. The stack of rings sits just above the primary mirror and serves to shield the instruments below from stray light.


The telescope enclosure building (above) and instrument room (below) jut out from the mountainside. The SDSS telescope facility was designed this way to provide the calmest and coldest possible air above and around the survey telescope.


A look down inside the 2.5-meter survey telescope reveals the primary mirror(the reflective surface at the bottom) as well as the secondary mirror (center), all surrounded by the wind baffle.


The 2.5-meter diameter primary mirror of the SDSS telescope. This photo was taken with the telescope horizontally on its side, pointing into the trees.


The SDSS 2.5-meter telescope.

2.5 Meter Telescoope

Apache Point Observatory in the Sacramento Mountains of New Mexico. The Sloan Digital Sky Survey's 2.5-meter telescope is on the left. White Sands National Monument is visible in the distance, above the telescope. The monitor telescope, used for calibrations, is inside the small dome to the right of center. Optical fibers for spectroscopy are pre-positioned each day in the building on the right (behind the trees). The building in the center rolls on rails to cover the 2.5-meter telescope when i t is not in use.


The secondary mirror of the 2.5-meter telescope.

Feedback map

If you gained information in your session which was not covered in the feedback, please take a look at these sites:

More info for the Sloan Digital Sky Survey

LA Times Story


Also - If you go to Google Earth and enter the following coordinates
you can get a better idea of the area
32º 47'17.81" N
105º 49'09.50" W
Elevation 2800 Meters

Many thanks to Ray McClure for suggesting this target and for writing the code to post it to the website.