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Introduction to extracting catalogues from the SHS

Currently selection of object catalogues is solely by equatorial (RA/DEC) co-ordinates. Selection by Galactic (l,b) co-ordinates (already allowed for pixel image extractions) will be implemented in a future release.

Given 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 Galactic Plane survey waveband 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).

At the moment only the matching H-alpha and contemporaneous SR wavebands are available from the new AAO/UKST Galactic Plane survey (taken on Tech-Pan films on 4-degree field centres). In due course the earlier I/SR surveys of the Galactic Plane taken between 1978 & 1985 will also be incorporated (these were taken on standard 5-degree field centres on IV-N and IIIaF plates) which will enable valuable colour information and proper motions to be provided.

Most of the object parameters returned are derived from the measurement in the primary waveband selected on the form (ie. either H-alpha or SR). Magnitudes in the other secondary waveband and other useful IAM parameters are also returned where available.

To facilitate a smooth upgrade path placeholders for various IAM parameters for the first epoch SR and I band data are incorporated into the default IAM catalogue listings attached to any pixel map extracted (with Null entries) until the older data is matched in.

The extraction software works across survey 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 Galactic Plane survey exposure(s) must have been measured and put on-line. Some films have not yet be taken and/or scanned. A summary of scans currently available on-line can be found under sky coverage.

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