Starlink Project
Starlink Cookbook 17.1

A.C. Davenhall & P.W. Draper

31st December 2001

Copyright © 2001 Council for the Central Laboratory of the Research Councils

The GAIA Cookbook


GAIA (Graphical Astronomy and Image Analysis) is an interactive astronomical image display and analysis tool. It includes a comprehensive suite of facilities for displaying and manipulating images. It also has extensive facilities for the astronomical analysis of images, including: astrometric calibration, automatic object detection and aperture, optimal and surface photometry. GAIA can access images in most of the data formats common in astronomy and can also retrieve copies of remote images and catalogues via the Internet.

This cookbook is an introduction to GAIA. It describes the facilities that GAIA provides and gives some simple examples of their use. It refers to GAIA version 2.6 or higher.

Who Should Read this Cookbook?

This cookbook is aimed at astronomers who are new to GAIA, but who think that it might be useful in their work. It is not aimed at experienced users of GAIA, for whom the GAIA manual (SUN/214) or the on-line help within GAIA itself might be more useful.


1 Introduction
 1.1 GAIA and SkyCat
2 Typographic Conventions
3 Facilities Available
 3.1 Image Display
 3.2 Image Analysis
 3.3 Catalogues and Online Resources
4 Data Formats
 4.1 World coordinate systems
 4.2 Catalogue formats
5 Starting GAIA
 5.1 Using GAIA from IRAF
 5.2 Multiple image files and image sections
 5.3 Demonstration mode
6 Obtaining Assistance
7 Introduction
8 Displaying an Image
9 Retrieving Remote Images and Catalogues
 9.1 Restoring catalogue access
 9.2 Using a proxy server
10 Using World Coordinates
 10.1 Reading off the Right Ascension and Declination
 10.2 Showing celestial coordinate grids
 10.3 Measuring angular separation
11 Superimposing and Contouring Images
 11.1 Contouring the displayed image
12 Astrometric Calibration
 12.1 Finding astrometric reference stars
 12.2 Creating a preliminary transformation
 12.3 Creating an accurate astrometric calibration
 12.4 Variations
13 Automatic Object Detection
14 Measuring Instrumental Magnitudes


Thanks to Martin Bly and David Berry for useful discussions and/or comments on the draft. The recipe in Section 12 is based on one originally written by David Berry and the one in Section 14 on one originally written by John Palmer. Karen Moran kindly unearthed the contact details for Twin Press.

Any mistakes, of course, are our own.


[1]   D.S. Berry and T.M. Gledhill, 26 October 2001, SUN/223.6: POLPACK — An Imaging Polarimetry Reduction Package, Starlink.

[2]   E. Bertin and S. Arnouts, 1996, Astron. Astrophys. Suppl, 117, pp393-404.

[3]   A.J. Chipperfield and P.W. Draper, 14 September 2001, SUN/226.4: EXTRACTOR — An Astronomical Source Detection Program, Starlink.

[4]   M.J. Currie, G.J.Privett, A.J.Chipperfield, D.S. Berry and A.C. Davenhall, 1 November 2001, SUN/55.16: CONVERT — A Format-conversion Package, Starlink.

[5]   A.C. Davenhall, 4 November 2001, SUN/190.10: CURSA — Catalogue and Table Manipulation Applications, Starlink.

[6]   A.C. Davenhall, 26 July 2000, SSN/75.1: Writing Catalogue and Image Servers for GAIA and CURSA, Starlink.

[7]   A.C. Davenhall, G.J. Privett and M.B. Taylor, 16 August 2001, SC/5.3: The 2-D CCD Data Reduction Cookbook, Starlink.

[8]   P.W. Draper, N. Gray and D.S. Berry, 13 September 2001, SUN/214.9: GAIA — Graphical Astronomy and Image Analysis Tool, Starlink.

[9]   P.W. Draper, M.B. Taylor and A. Allan, 22 October 2001, SUN/139.15: CCDPACK — CCD data reduction package, Starlink.

[10]   N. Eaton, P.W. Draper and A. Allan, 30 December 2000, SUN/45.12: PHOTOM – A Photometry Package, Starlink.

[11]   W. Jaffe, 1998, Astronomical Images (Twin Press: Vledder) CD-ROM. To contact Twin Press send an electronic mail message to G. Kiers ( See URL:

[12]   D.C. Kay and J.R. Levine, 1995, Graphics File Formats, second edition
(Windcrest/McGraw-Hill: New York). See in particular Chapter 18, pp235-244.

[13]   D. Monet, A. Bird, B. Canzian, H. Harris, N. Reid, A. Rhodes, S. Sell, H. Ables, C. Dahn, H. Guetter, A. Henden, S. Leggett, H. Levison, C. Luginbuhl, J. Martini, A. Monet, J. Pier, B. Riepe, R. Stone, F. Vrba and R. Walker, 1996, USNO-SA1.0, (U.S. Naval Observatory: Washington DC). See also URL:

[14]   R. Morris and G.J. Privett, 6 December 1996, SUN/166.4: SAOIMAGE — Astronomical Image Display, Starlink.

[15]   R. Morris, G.J. Privett and A.C. Davenhall, 2 December 1999, SG/12.2: An Introduction to IRAF, Starlink.

[16]   J. Palmer and A.C. Davenhall, 31 August 2001, SC/6.4: The CCD Photometric Calibration Cookbook, Starlink.

[17]   G.H. de Vaucouleurs, A. de Vaucouleurs, H.G. Corwin, R.J. Buta, G. Paturel and P. Fouqué, Third Reference Catalogue of Bright Galaxies, 1991 (Springer: New York).

[18]   P.T. Wallace, 21 June 1995, SUN/56.10: COCO — Conversion of Celestial Coordinates, Starlink.

[19]   R.F. Warren-Smith, 11 January 2000, SUN/33.7: NDF — Routines for Accessing the Extensible N-Dimensional Data Format, Starlink.

[20]   R.F. Warren-Smith and D.S. Berry, 23 October 2001, SUN/210.11: AST — A Library for Handling World Coordinate Systems in Astronomy (Fortran Version), Starlink.

[21]   R.F. Warren-Smith and D.S. Berry, 23 October 2001, SUN/211.11: AST — A Library for Handling World Coordinate Systems in Astronomy (C Version), Starlink.

[22]   R.F. Warren-Smith and D.S. Berry, 17 July 2000, SSN/20.3: Adding Format Conversion Facilities to the NDF Data Access Library, Starlink.

[23]   D.C. Wells, E.W. Greisen and R.H. Harten, 1981, Astron. Astrophys. Suppl, 44, pp363-370.