SoG Image Viewer
As described above, most of the activation actions you can define result in a viewer window popping up to display an image or spectrum. Exactly what kind of viewer is shown depends on how TOPCAT is set up.
The default image viewer is SoG, an astronomical image viewer based on JSky, which offers colourmap manipulation, image zooming, graphics overlays, and other features. For this to work JAI, otherwise known as Java Advanced Imaging must be installed. JAI is a free component available from Sun, but not a part of the Java 2 Standard Edition by default. If JAI or the SoG classes themselves are absent, a fallback viewer which just displays the given image in a basic graphics window with no manipulation facilities is used. The two possibilities are displayed below:
SoG Image Viewer
Fallback Image Viewer
The default spectrum viewer is SPLAT, a sophisticated multi-spectrum analysis program. This requires the presence of a component called JNIAST, which may or may not have been installed with TOPCAT (it depends on some non-Java, i.e. platform-specific code). There is currently no fallback spectrum viewer, so if JNIAST is not present, then spectra cannot be displayed. In this case it will not be possible to select the Display Named Spectrum item in the Activation Window. An example of SPLAT display of multiple spectra is shown below.
SPLAT Spectrum Viewer