The Simple Image Access web service conducts a position based search of the Chandra Source Catalog. One specifies the RA, DEC, and search radius (SR) in decimal degrees and receives one of three available result sets based on the value of the verbosity (VERB) parameter. The service implements the IVOA Simple Image Access Specification (v1.0).

The base URL of the Chandra Source Catalog Simple Image Access is

http://cda.cfa.harvard.edu/csc21siap/queryImages

The service accepts the following parameters in the HTTP query:

• POS - Right Ascension and Declination expressed as a comma separated pair in decimal degrees
• SIZE - Angular size of the search region in decimal degrees
  • Comma separated pair of values are interpreted as the angular width of the right ascension and declination axes respectively
  • Single value is interpreted as the angular width along both the right ascension and declination axes
• FORMAT - Format of the images referenced in the output table. The following values are allowed:
  • image/fits - FITS image filetype
  • image/jpg - JPEG image filetype
  • ALL - All image filetype
• VERB - Verbosity of the result set. Defaults to 3. The following values are allowed:
  • 0 - A minimal result set
  • 1 - Additional information to uniquely describe the images
  • 2 - Contains metadata defining all query constraints
  • 3 - A maximal result set

An image access request may be executed on the Unix command line using the HTTP query syntax with a command-line tool such as cURL or Wget. A VO image search on the position 246.7925, -24.32027, using a search region 1.66 decimal degrees in both right ascension and declination and verbosity level 2, would appear as follows, where we perform the query using Wget:

wget -O out.vot 'http://cda.cfa.harvard.edu/csc21siap/queryImages?POS=246.7925,-24.32027&SIZE=1.66&VERB=2'

Alternatively, a form has been provided which will perform a Simple Image Access search.