The Sloan Digital Sky Survey Legacy Imaging Project provides wide-field imaging and ugriz photometry for 14,055 square degrees of sky in the northern hemisphere. This page describes an overview of the survey, and links to tutorials and reference material that will help users of SDSS Imaging data to identify and retrieve relevant products.

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SDSS Imaging Overview

Survey Summary

The Sloan Digital Sky Survey Legacy Imaging Project operated between September 19, 1998 and November 18, 2009 collecting wide-field imaging for 14,055 square degrees of sky (about 1/3 of the entire sky). The spatial footprint for the SDSS Legacy Imaging survey is shown in Figure 1. The imaging frames have a sampling resolution of 0.396 arcsec/pixel and the survey utilized five broadband filters (ugriz) to cover a total wavelength range of 3551-8931 Å. The derived catalog includes photometry for almost half a billion unique sources.

Figure 1 - Spatial footprint of the SDSS Legacy Imaging data.

Telescopes & Instrumentation

SDSS Legacy Imaging data were obtained at the Apache Point Observatory in New Mexico using the SDSS-2.5m telescope (Gunn et al. 2006) using the SDSS Photometric Camera (Gunn et al. 1998). The SDSS camera operated by scanning the sky in long stripes that were in 2.5 degrees wide, referred to as runs. Each scanline includes data from all five filters, ugriz, and is divided into fields which are 10 by 13 arcminutes of sky (2048 by 1489 pixels). Each field can be uniquely identified by a sequence of three numbers:

  • the run number, which identifies the specific scan,
  • the camera column, or "camcol," a number from 1 to 6, identifying the scanline within the run, and
  • the field number. The field number typically starts at 11 (after an initial rampup time), and can be as large as 800 for particularly long runs.

Additional information about the instrumentation for this survey can be found in the SDSS documentation.

Data Products and Access

The Legacy Imaging data products are available for download through several MAST interfaces, including the MAST Portal and programmatically in Python through astroquery.mast. For information on how to access and download SDSS data through MAST,  please refer to the Data Access page. 

MAST has archived the high-level "science ready" data products from the SDSS survey. The  Legacy Imaging Data Products page contains details on which files are available at MAST, which includes the individual frame images for all five filters and summary catalog files containing observation metadata and measurements from the SDSS Imaging Pipeline.


For Further Reading...

Citations and Acknowledgements

Refer to the SDSS Surveys page for instructions on how to cite this document and acknowledge the use of data obtained from MAST in publications.

For other SDSS Imaging citations, please refer to the relevant section of the SDSS Technical Papers list. These include: