TOPCAT

TOPCAT (Tool for OPerations on Catalogues And Tables) is a Java-based desktop application for the interactive analysis of astronomical catalogues and tabular data. It is widely used by astronomers to explore, compare, and visualize large tabular datasets.

Key capabilities include interactive plotting, with 2D scatter plots, histograms, and density plots, plus 3D visualizations. Plotting supports customization of axes, scales, symbol sizes, and color mappings, and users can select regions directly on plots. The software offers extensive table operations, such as sorting, filtering, joining, and computing new columns from expressions that reference existing columns and units.

TOPCAT provides robust data-management tools, including cross-matching of tables, statistics, and data summarization. It is designed to handle large catalogs efficiently and supports data provenance and units.

Interoperability is a key focus: TOPCAT reads and writes widely used astronomical formats such as FITS and VOTable, and VO standards, and it supports the Simple Application Messaging Protocol (SAMP) to communicate with other applications in the Virtual Observatory ecosystem. It is commonly used with STILTS, a related set of command-line tools for batch processing and scripting.

Platform and availability: TOPCAT runs on Windows, macOS, and Linux systems via the Java Runtime Environment. It is free and open-source software, with documentation and tutorials available from its official site.