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What is TOPCAT?

TOPCAT is an interactive graphical viewer and editor for tabular data. Its aim is to provide most of the facilities that astronomers need for analysis and manipulation of source catalogues and other tables, though it can be used for non-astronomical data as well. It understands a number of different astronomically important formats (including FITS and VOTable) and more formats can be added.

It offers a variety of ways to view and analyse tables, including a browser for the cell data themselves, viewers for information about table and column metadata, and facilities for 1-, 2-, 3- and higher-dimensional visualisation, calculating statistics and joining tables using flexible matching algorithms. Using a powerful and extensible Java-based expression language new columns can be defined and row subsets selected for separate analysis. Table data and metadata can be edited and the resulting modified table can be written out in a wide range of output formats.

It is a stand-alone application which works quite happily with no network connection. However, because it uses Virtual Observatory (VO) standards, it can cooperate smoothly with other tools in the VO world, such as AstroGrid's VODesktop and CDS's Aladin. TOPCAT is currently developed within the AstroGrid project, and is offered as part of a standard suite of applications on the AstroGrid web site, where you can find information on several other VO tools.

The program is written in pure Java and available under the GNU General Public Licence. It was initially developed within the now-terminated Starlink project in the UK, and is currently developed and supported by its author as part of the AstroGrid project. Its underlying table processing facilities are provided by STIL.


Full tutorial and reference documentation for TOPCAT is provided by SUN/253, the user document. This is available within the program at runtime via the context-sensitive help system, or in the following forms within the distribution or on the web:


You can see screenshots of TOPCAT in action in the following places:

  • The TOPCAT gallery is a page containing lots of window screenshots
  • The TOPCAT V3 screenshots page showcases some of the features introduced at version 3 (July, August 2007)
  • SUN/253's windows appendix details all of TOPCAT's windows with illustrations
  • There's a montage of some of the windows TOPCAT provides below; click on it for a full size version

* Obtaining TOPCAT

TOPCAT is written in the Java language using the Java 2 Standard Edition version 1.4 and should run on any J2SE 1.4, 1.5 or 1.6 system. This means it can be run on a wide range of platforms, without requiring any recompilation - you just need to ensure that you have a suitable Java Runtime Environment (JRE). If you have Java installed, but are unsure which version, you can find out by doing something like "java -version" - if it says 1.4.something or 1.5.something you should be OK. If you don't have Java installed, or have the wrong version, you can obtain it for Linux, Solaris and MS Windows from Sun's web site (you only need the "JRE" rather than the "SDK" download, unless you will be doing development work). J2SE Runtime Enviroments (sometimes called JVM or Java Virtual Machines) for other platforms may be available from operating system vendors; in particular TOPCAT is known to run (though not currently exhaustively tested) on MacOS X (see here).

Note GNU's java (gij) does not work well at time of writing - this is sometimes bundled with Linux distributions. If you have this, you are advised to get the Sun implementation instead.

Having got Java, There are several ways to download TOPCAT, described in rough order of advisability in the following subsections. More information on how to run the program having obtained it can be found in SUN/253's section on Invoking TOPCAT.

Standalone Jar File

The most convenient form for downloading is to pick up a single Jar file containing the required classes:

(Note: if you try to download these directly your browser may say something about a failed security check. Make sure that you save it to a file, for instance by using shift-click in Netscape).

On Unix-like operating systems, download one or other of these jar files and the startup script topcat into the same directory chmod +x topcat, and you can just run the command:

On non-Unix systems the script won't work, and you can use a command like:
   java -jar topcat-*.jar
or invoke it in some other system-dependent way such as by clicking on it.

For many users, topcat-lite will provide all the features they need. The optional extras provided by topcat-full include:

  • Treeview-like hierarchy browsing
  • SoG image viewer (though you still need JAI for it to work)
  • MySpace and SRB remote file browsing for table load/save
  • VO-related load dialogues for Cone Search, SIAP & Registry Query
Even topcat-full lacks a few of the full set of features (SPLAT spectrum viewer, proper coordinate handling in SoG), since these require native libraries; for these you will need the Full Starjava installation described below.

WebStart is a Java technology which enables one-click download, installation, updating and invocation of Java applications over the web. If you have Java's WebStart installed, you can install and invoke TOPCAT in one click from one of the following links:

The first of these can be used for your own data, but will prompt for confirmation with a dire warning that you are running untrusted code (it's OK - trust me!). The second is just a demo with some example tables to play with that will run in a restricted environment, so it can't load or save tables. It also does not permit use of user-defined algebraic expressions to create synthetic columns or subsets; there may be other restrictions too. See the comments in the previous item for the difference between topcat-lite and topcat-full.
Full Starjava Installation

If you want the most comprehensive installation then download and unpack the full starjava tree in one of the following forms:

These archives include related applications such as SPLAT, SoG and Treeview, some of which form optional plugins for TOPCAT (e.g. SPLAT as a spectrum viewer). You can run TOPCAT using the starjava/bin/topcat script (Unix) or by running java -jar starjava/lib/topcat/topcat.jar.

If you have a Macintosh, you can pick up the following for easy installation:

topcat-full.dmg (19.0M)

TOPCAT is currently (2009) under active, though intermittent, development, and I'm very open to user feedback. Any comments, questions, requests, bugs, job offers etc, please contact me:

  • Author: Mark Taylor, Astrophysics Group, Physics Department, Bristol University
  • Email: Cette adresse email est protégée contre les robots des spammeurs, vous devez activer Javascript pour la voir.
  • TOPCAT WWW page:
Mise à jour le Lundi, 02 Novembre 2009 10:28