### 5 Using GAIA and EXTRACTOR

The Graphical Astronomy and Image Analysis Tool (GAIA - SUN/214), has an interactive toolbox facility that uses the EXTRACTOR (and SExtractor) programs. This allows you to interactively adjust the detection preferences and identifies the objects that have been detected by drawing suitable ellipses over your image (in fact GAIA produced the image used on the title page of this document).

GAIA also displays the results catalogue so you can view the measurements associated with each object and vice versa (i.e. you can select one of the displayed ellipses and view the associated measurements, or select a row of measurements and view the associated object). The catalogue interface also allows you to sort and select objects on the basis of their measurements.