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 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, services and datasets in the VO world and beyond.
The program is written in pure Java and available under the GNU General Public Licence. It has been developed mostly in the UK within various UK and Euro-VO projects (Starlink, AstroGrid, VOTech, AIDA, GAVO) and under PPARC and STFC grants. Its underlying table processing facilities are provided by the related library STIL.
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:
subscribe topcat-user" or "
subscribe topcat-announce" to firstname.lastname@example.org, or use the Subscribe link on the pages linked above. Archives are available from those pages. There is a bit more information on the mailing list page.
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 1.5 and should run on any J2SE 1.5 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 it for Linux, Solaris and MS Windows from Oracle'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 on MacOS X.
Note Various open-source java implementations
gij, OpenJDK-based implementations) do not always
work well at time of writing - these are sometimes bundled
with Linux distributions.
If you have one of these (try
java -version to find out)
and are experiencing trouble with TOPCAT,
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.
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 hierachy view), 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:
If you have a Macintosh, you can pick up the following for easy installation:
topcat-full.dmg (29.4M)A couple of FAQ entries are relevant: how to set flags for memory usage etc and problem with "damaged" dmg file.
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.
The most recent public release of TOPCAT is version 4.0-1, released 1 July 2013.
For a detailed history of the changes in this and previous releases, see the
Full Version Historysection of SUN/253.
TOPCAT is currently (2013) under active development, and I'm very open to user feedback. Any comments, questions, requests, bugs, job offers etc, please either post to the topcat-user list or contact me direct: