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Tools for data access

DR4 data are distributed via the Catalog Archive Server (CAS), an SQL database with fast search capabilities, and the Data Archive Server (DAS), a collection of fits images and tables containing the outputs of the imaging and spectroscopic reduction pipelines. In addition, the SDSS collaboration has created catalogs and other data products based on public survey data that we link from our Value Added Data Products page.

Catalog Archive Server (CAS) Search

Web interfaces

Catalog Archive Server (CAS) The Catalog Archive Server offers efficient search tools for querying the imaging and spectro catalogs from SDSS.
Spectro Query Server Search spectra by position, or by spectral or photometric parameters. Retrieve survey files.
Imaging Query Server Search photometry catalog by position or by photometric parameters. Retrieve survey files.
SpecList Upload plate,MJD,fiber list as part of a SQL query
Imaging cross-ID Find SDSS matches for a list of objects.
SQL search Directly search the database using your own SQL queries (also see skyserver help pages).
CasJobs Use this batch job server for direct SQL searches of the database with generous timeout setting. Share result sets with your collaborators.
Navigate Point and click on SDSS images.
Finding charts Generate jpeg finding charts from SDSS images.
Image lists Get jpeg cutouts of SDSS imaging for object lists with link to finding chart. Option to generate object list from SQL query.

Query clients

In addition to using the web interfaces above, you can directly connect to the database server to perform your own SQL queries using these clients.

sdssQA Provides GUI to edit and submit SQL queries
sqlcl python script to submit SQL queries from the command-line
skyserver.el Submit SQL queries from an emacs buffer

Data Archive Server (DAS)

The DAS contains

  • images of the night sky ("corrected frames") in fits and jpeg format
  • calibrated object lists with photometric parameters as fits binary tables
  • reduced spectra and spectral parameters as fits binary tables and ps/gif plots

Files and directories within the DAS are designated by survey identifiers of the desired data: run/rerun/camcol/field for imaging; plate/MJD/fiberID for spectroscopy. The easiest way to obtain this designation is by one of the query forms provided. The DAS is described in detail on the DAS structure and contents page.


FOOT DR4 Check whether coordinate is in DR4 for arbitrary (list of) RA,DECs; if so, retrieve run,rerun,camcol,field,rowc,colc


DAS retrieval form Use query forms above to obtain survey designation of required data to be uploaded here. Small result sets will be returned as .tar or .zip archive; larger sets can be downloaded using http or rsync (see rsync help). The coverage page explains runs, reruns etc.
http access to DAS Recommended method for creating new whole or partial mirrors and individually selecting specific files. Use your web browser or other http clients like wget.
Recommended options for wget to mirror entire directories:
--no-host-directories -l inf -r -np --continue
rsync server Recommended method to updating existing mirrors. The rsync URL is rsync://dr4@rsync.sdss.org/DR4. See the rsync help page.
Spectra in bulk Get all spectroscopic data, or redshift lists by object type (galaxies, quasars, stars)

Last modified: Wed Jun 29 17:23:14 CDT 2005