Introduction to Astronomy Data Manipulation and Visualisation

This session forms part of the astronomy strand of the residential module DISC6001 along with the session TOPCAT: A powerful Tool for OPerations on Catalogues And Tables and will be led by Yannick Roehlly.

Aims & Objectives

The aim of the session is to introduce students with common tools to interact with tabular data (catalogues), images, and spectra.  We will also cover online databases and how to query them, as well as the concept of “Virtual Observatory”. At the end of the session, the students should:

  • have Topcat, Aladin, and VOSpec installed;

  • know how to load a catalogue in Topcat or an image in Aladin;

  • send tabular information from Topcat to Aladin;

  • use Aladin to get additional information about the objects on the image or to add “visual information” to objects they have in a table;

  • query online databases like Vizier or SDSS;

  • know a little about querying on-line database programmatically with Python.


Part 1: the software

  • Installation of the various programmes on the student computers.

  • Quick presentation of Topcat to manipulate tabular data and stilts which is a command-line version of Topcat.

  • Quick presentation of VOSpec to manipulate spectra. Given that the spectra file formats are quite complex and that the lecturer is not an expert on  the subject, students with special need should contact him before the course.

  • Using the Aladin Sky Atlas:

    • Image visualisation and basic manipulations;

    • Sending tabular data from Topcat to Aladin using the Simple Application Messaging Protocol (SAMP). We will show that this also works with DS9 which is another tool to manipulate image data.

    • Getting on-line data directly from inside Aladin: new images, identification of objects.

    • Overlapping different images.

  • Quick presentation of other software of interest: Glue, Vaex (for large dataset manipulation).


Part 2: the on-line databases

  • Presentation of some on-line database and on the way to query them.

  • General presentation of the Virtual Observatory (VO).

  • Accessing the virtual observatory using Topcat.

  • Accessing the VO programmatically with Python.

At every stage, sample data may be provided to students to manipulate on your own computer but it's better if you bring their own data if you have it.


Prerequisites / Linked Modules

Students must have a computer with Java installed (Topcat and Aladin are Java applications).  Some time will be taken to install the software on the computers at the beginning of the course.

Students should register on SciServer ( in order to be able to make some queries on SDSS.

Students interested in using Python to query the Virtual Observatory should have Python installed.  For those who are not Python “experts”, the easiest way is to use the Anaconda Python distribution.







CDS Portal:

SDSS CasJobs:


Learning & Teaching Resources

Students are encouraged to bring the data - catalogue or images - they are or will be working on during their PhD.  If they don't have it they may talk to their tutor to know what kind of data they will have to work on so the can get it from on-line databases.