Search Tools

You can search the SDSS database with a query. A query is a request for information. You specify what data you want, and what conditions you want the data to satisfy. For example, you might ask the database to return the positions of all stars brighter than a certain magnitude in a certain filter.

To search the database, select one of the following tools

• Radial:  Search the sky around a given point (EASY)
• Rectangular:  Search the sky in a rectangular region (EASY)
• SQL:  Type in a SQL query directly (HARDEST)

Search Tools for scientists

• Imaging Query:  Form-based query on imaging data
• Spectroscopic Query:  Form-based query on spectroscopic data
• IR Spectroscopic Query:  Form-based query on IR spectroscopic data

The names and units of fields on the query pages

• ra, dec are the sky coordinates of the search.
  • They can be entered either in degrees or in the h:m:s, d:m:s notation.
• radius is the search radius for a radial query.
  • It is measured in minutes of arc.
• u,g,r,i,z are the magnitudes of the objects in the SDSS.
  
  • These represent the fluxes of light measured in logarithmic units, through various wavebands from the ultraviolet to the infrared

The output options and formats on the query pages

• Return: the number of objects
  
  • Selecting all will return all objects
    
  • Selecting top N will return the first N objects satisfying the query
• Format: the output format
  
  • It can be HTML, when a formatted web page is returned
    
  • It can be CSV, when a comma separated, unformatted text is returned, with one header line and subsequent objects in a new line, attributed separated by a comma
    
  • It can be XML, not yet implemented

Getting FITS files from the SAS

You can easily retrieve the raw FITS file data corresponding to your query using any of the CAS search tools. If the necessary columns are included in the SELECT part of your query, the appropriate button will automatically appear on the query results page (below the query results) to allow you to upload the appropriate information to the SAS (Science Archive Server). These columns are part of the default query in each of the search tools, but if you modify the default query or enter your own query, be sure to include the following columns:

• run, rerun, camcol, field from the PhotoObj (or PhotoTag) tables if you want imaging FITS data from the SAS;
• plate, mjd, fiberid from the SpecObj or SpecPhoto tables if you want FITS spectra from the SAS.

Query timeout and row limits

All queries are subject to a 10min timeout, and a maximum of 500,000 returned rows, whichever happens first.