Where to start

Data Release 7 is the final data release of the Sloan Digital Sky Survey. This site gives information for how to work with Data Release 7 data. The best way to navigate the site is to use the link on the left-hand menu. The list below shows what each of those links means.

• Go to sdss.org - links back to the main Sloan Digital Sky Survey website, which has a general introduction to the science and its science
• DR7 Home - the home page of the Data Release 7 site
• Where to Start - this page, which gives advice on how to get started with using SDSS DR7 data
• Data Access - an introduction to the methods by which you can access SDSS DR7 data
  
• Database (CAS) - access to the catalog database of the SDSS, where you can find numerical data such as magnitudes
• Files (DAS) - access to SDSS data files in FITS format
• Value-Added - access to SDSS value-added catalogs, useful catalogs derived from DR7 data
• Tutorials - guides to solving common problems in astronomy using SDSS data
• Older Releases - access to previous data releases from the SDSS
• About DR7 - provides information on what data are contained in Data Release 7
  
• Instruments - descriptions of the instruments that the SDSS used in its observations
• Data Processing - descriptions of the processing that SDSS data go through between initial observation at the telescope and final data release online
• Algorithms - detailed information about the algorithms that the SDSS uses to process data
• Help - information and links for help on how to use SDSS data
  
• FAQ - frequently asked questions about the SDSS and how to use its data
• Glossary - definitions of key terms used by the SDSS
• DR Papers - papers describing each data release of the SDSS; these papers are the fundamental source of information about how to use SDSS data
• Helpdesk - links to a page where you can ask questions about the SDSS; an expert will get back to you with answers
• Search - a tool for searching the Data Release 7 website

About the data

• Acknowledging the use of SDSS data
• Searching for SDSS catalog data: The Archive Intro page of the Catalog Archive Server contains a high-level description of what catalog data the SDSS provides, and how the databases are organized. The most searchable detailed lists are the table descriptions in the schema browser. The most commonly used data are in the following tables:
  • Photometry: PhotoTag, PhotoObj, PhotoAux
  • Spectroscopy: SpecObj, SpecLine
  • Both: SpecPhoto
  The algorithms page describes how the most important SDSS quantities are measured, and thus also gives an overview of what is available.
• The Early Data Release (EDR) paper (with a journal subscription, access the EDR paper at the AJ web site) is the most comprehensive printed description of SDSS data. Much of the information on this web site is based on the EDR paper. It should be considered essential reading to do science with SDSS data.
• However, some of the information in the EDR paper has been superseded by information on this web site. There is a description of changes from the Early Data Release to Data Release 1 (DR1) at the DR1 site (also see the DR1 paper Abazajian et al. 2003, AJ 126, 2081.
• DR2: The DR2 paper (Abazajian et al. 2004, AJ, 128, 502) contains the details, and the respective sections of this web site have been updated accordingly. The most important change is that the DR1 contained the "beta" processing of survey data. DR2 has bug-free photometry and vastly improved spectrophotometry -- see About DR2 on the DR2 site for details.
• About DR3 gives an overview of what DR3 contains, and a summary of the improvements in DR3 compared to earlier data releases. The DR3 paper (Abazajian et al. 2004, AJ 129, 1755) (available here as DR3.ps (2.6 MB)) gives a brief overview of the changes introduced in DR3.
• About DR4 briefly describes the contents of DR4, caveats for use of DR4 data, and upcoming features. There is also a DR4 paper (Adelman-McCarthy et al. 2006, ApJS 162, 38).
• About DR5 describes the contents of DR5; there is a DR5 paper, Adelman-McCarthy et al. 2007, ApJ Supplements, in press [arXiv link].
• About DR6 describes the contents of DR6.
• About DR7 describes the contents of DR7

Avoiding Common Pitfalls when Using the Data

• These pages help to avoid the most common pitfalls in retrieving and using SDSS data:

  • When you use the photometric object catalogs, you must check the photometric object flags to obtain meaningful results. See the tutorial How do I find out if SDSS's imaging data for an object are reliable? for more information on how to use these flags.
  • When you use the spectroscopic catalogs, the photometric flag checking has been done as part of target selection. However, you must check the redshift status flag to exclude non-secure identifications and redshifts.
  • When you use the SQL database of the Catalog Archive Server (CAS), please read the advice on optimising CAS queries to avoid unnecessarily slow queries.

  Other caveats are detailed on the individual pages for each of our data products and on the Known Problems page.

About the Sloan Digital Sky Survey

• The SDSS Project book, which includes a detailed scientific justification, and comprehensive descriptions of the hardware.
• The York et al. technical summary paper of SDSS. You can access York et al. 2002 locally and via ADS at York et al. 2000
• The SDSS publication list, including
  • technical publications
  • scientific publications by members of the collaboration
  • publications based on SDSS data written by people outside the collaboration