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, VOTable and CDF) and more formats can be added. It is especially good at interactive exploration of large (multi-million row, lots of columns) tables.
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 sophisticated interactive 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, services and datasets in the VO world and beyond.
The program is written in pure Java and available under the GNU General Public Licence, though some of the library code is LGPL. It has been developed mostly in the UK within various UK and Euro-VO projects (Starlink, AstroGrid, VOTech, AIDA, GAVO, GENIUS, DPAC) and under PPARC and STFC grants. Its underlying table processing facilities are provided by the related packages STIL and STILTS.
The following is a list of the program's main capabilities. The hyperlinks are to the relevant parts of the user document.
Supported table input formats include:
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 and searchable help system, or in the following forms within the distribution or on the web:
A list of frequently asked questions is available. If you want to suggest additional questions and/or answers, please get in touch.
Two mailing lists are in use for TOPCAT and related software:
firstname.lastname@example.org: Public list for questions, answers, discussions, bugs, comments, ...
email@example.com: Low-volume read-only list for release announcements and news items.
If you have queries or support enquiries you are encouraged to
send them to
topcat-user. However, I can still
answer mail directly to
me if you prefer that.
You can see screenshots of TOPCAT in action in the following places:
TOPCAT is written in the Java language using the Java 2 Standard Edition version 8, and should run on any Java SE 8 or more recent 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 don't have Java installed, or have an unsuitable version, you can obtain the Java SE for Linux, Mac OS X, MS Windows and Solaris from Oracle's web site (you only need the "JRE" rather than the "JDK" download, unless you will be doing development work). Java SE Runtime Enviroments (sometimes called JVMs or Java Virtual Machines) for other platforms may be available from operating system vendors. OpenJDK is also suitable.
If starting TOPCAT fails with an error like
you have a version of Java that is too old, and you should
upgrade to Java 8 or later.
If you're unable or unwilling to do that and you only have the
rather ancient Java 6, you can still use TOPCAT version
v4.6-3 or older.
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.
The most convenient form for downloading is to pick up a single Jar file containing the required classes:
On Unix-like operating systems, download one or other of these
jar files and the startup script
into the same directory, then "
chmod +x topcat",
and you can just run the command:
topcatOn non-Unix systems the script won't work, and you can use a command like:
java -jar topcat-*.jaror 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-fulllacks a few of the niche features (proper coordinate handling in SoG, NDF viewing in hierarchy view, parquet support), since these require native libraries; for these you will need the Full Starjava installation described below, or
topcat-extraif you just want parquet.
If you have an Apple Mac, you can pick up the following for easy installation:
topcat-full.dmg (43.4M)A couple of FAQ entries are relevant: how to set flags for memory usage etc and problem with "damaged" dmg file.
WebStart is a Java technology which enables one-click download, installation, updating and invocation of Java applications over the web. It's quite convenient, but somewhat deprecated or completely missing in more recent versions of Java, and sometimes doesn't work properly. If you have Java's WebStart installed, you can install and invoke TOPCAT in one click from one of the following links:
When it works well, WebStart can make download and running very easy. Sometimes however it seems to cause trouble that is difficult to diagnose, and it's also being phased out in later Java versions, so the standalone jar file is generally recommended instead.
If you want the most comprehensive installation then download and unpack the full starjava tree in one of the following forms:
starjava/bin/topcatscript (Unix) or by running
java -jar starjava/lib/topcat/topcat.jar.
Note that TOPCAT is also packaged as part of the Debian Astro bundle - see the FAQ.
The most recent public release of TOPCAT is version 4.8-2, released 15 October 2021.
For a detailed history of the changes in this and previous releases, see the
Full Version Historysection of SUN/253.
TOPCAT is currently (2021) under active development, and I'm very open to user feedback. Any comments, questions, requests, bugs etc, please either post to the topcat-user list or contact me direct: