Introduction to extracting cataloguesGiven a free format RA & Dec (eg 01 10 34.2 -65 32 07), equinox (B1950 or J2000), the size of a rectangular or circular region to extract, the primary waveband/Schmidt survey required and a magnitude range the web-form, Get a Catalogue, returns a listing of the objects detected by SuperCOSMOS during its Image Analysis Mode (IAM). Most of the object parameters returned are derived from the measurement of the plate in the primary waveband selected on the form. Magnitudes in the other secondary wavebands and proper motions are also returned where available.
The extraction software works across plate/field boundaries and therefore large areas can be searched (up to 100 sq degrees).
The user can specify the output equinox, the output epoch and the format (ASCII, Tab, FITS) of the data returned. The tab-separated listing is compatible with the GAIA and CURSA software packages and is useful if you want to overlay the extracted objects on, for example, a radio pixel map (assuming the pixel data comes with a built in World Coordinate System).
Expert parameters are also available on the form. The default values will provide the user with a sensible catalogue that contains a minimum amount of spurious sources (for example areas around bright stars are excluded to prevent contamination from diffraction spikes and haloes).
For the form to successfully return data covering the entire region requested the relevant survey plate(s) must have been measured and put on-line. Some plates have not yet be taken and/or scanned. A summary of scans available on-line can be found under sky coverage.
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