SAOImageDS9 is a multi-platform tool, a Tk/Tcl program that enables visualizing astronomical images and analyzing complex FITS data.

With SAOImageDS9 you can easily open new FITS files and start examining the content within minutes. The tool also allows importing arrays, n-dimensional raster data (NRRD), flat-binary raster files (ENVI), and other types of visual elements in the following formats: GIF, TIFF, JPEG, and PNG.

After uploading your content, you have the general viewing panel, plus two smaller windows that allow visualizing the space orientation on the map, respectively, the frame, pixel-like objects (for in-detail lookup).

The tool enables frame adjustment on the map, different zooming in and out (with predefined levels), scale configuration, region focus and selection, or mask, graph, and crosshair parameter adjustments.

SAOImageDS9 is a powerful utility that offers accessibility, solid performance, and flexible design configuration. For example, when it comes to GUI changes, users can replace the light theme with the dark one, and they also have available controllers for the display of all windows, plots, and dialogs.

The app adds an overlay onto any loaded image. This overlay displays valuable configuration options and choices for filtering, sorting, and registering unique observations (from the catalog dialog's config options). Plus, with the new footprint server, users get increased compatibility with Chandra and Hubble Legacy Archive.

Last but not least, with the help of the built-in Prism feature, you can preview and analyze FITS file structures, examine all the extensions (including the headers and the table data), and generate 2D and histogram plots, straight from your column data.

To summarize, SAOImageDS9 is an excellent choice for anyone interested in conducting in-depth analysis in the astronomical field. A major plus are the following: the tool is free of cost, has rich documentation for understanding where to start learning, and is supported by the astronomical community (which is prolific for quality and assistance).