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Barth, A. J. 2001, in ASP Conf. Ser., Vol. 238, Astronomical Data Analysis Software and Systems X, eds. F. R. Harnden, Jr., F. A. Primini, & H. E. Payne (San Francisco: ASP), 385

ATV: An Image-Display Tool for IDL

Aaron J. Barth
Harvard-Smithsonian Center for Astrophysics


The IDL language offers a powerful environment for reduction and analysis of astronomical data. While there are numerous libraries of publicly available IDL routines, one major drawback has been the lack of an image-display program optimized for viewing astronomical images. ATV is a display program written entirely in IDL and designed to emulate the SAOimage and DS9 programs. It works equally well under the Unix, Linux, Windows, and MacOS versions of IDL, and includes features such as interactive control of color stretch, zoom, and image scaling; image blinking; and creation of publication-quality PostScript output. It also includes a simple photometry package suitable for quick-look reductions. The program is freely available via the Internet.

1. Introduction

Interactive Data Language (IDL) is an increasingly popular tool for astronomical data reduction and analysis. One long-standing drawback of IDL, for astronomical applications, has been the lack of a high-level display routine optimized for viewing astronomical images. IDL's built-in image display routines are primitive, and it is difficult to integrate stand-alone programs such as SAOimage and DS9 into an IDL session. ATV is an image-display program designed to solve this problem. It is written entirely in IDL and offers a range of features similar to the stand-alone image viewers.

Figure 1: The main ATV display window and the ATV photometry window.

ATV takes advantage of the IDL widget interface, which provides a simple mechanism for creating graphical user interfaces, as well as a number of preexisting routines in the IDL Astronomy User's Library. Thus, the ATV code itself is fairly compact, and in some respects it simply acts as a graphical front-end for various library routines. The initial release of the program in 1998 contained basic features such as control of image scaling and color stretch, blinking, and zooming, and since then the program has grown to include other features such as photometry, coordinate tracking, and creation of PostScript output. For IDL users, the major benefit of ATV is that it works within an IDL session, so the user can pass data or FITS filenames directly to ATV from the IDL command line. ATV can be customized to pass data to other IDL routines, and its internal data are stored in common blocks so that they can be accessed or modified by the user.

Since ATV is distributed as IDL source code, it can easily be modified for specialized use. For example, it has been adapted for displaying data from the FUSE satellite (, and a modified version of ATV is being used as part of the CEDAR software suite for the HST Cosmic Origins Spectrograph (Béland & Penton, this volume).

2. Features

The main ATV window is designed to look similar to SAOimage and DS9, with a panning window, a zoom window that tracks the cursor motion, and information boxes that track the pixel coordinates, pixel value, and world coordinates (Figure 1). ATV's features include:

3. Future Development Goals

Development of ATV continues with new versions released every few months. Some areas for future development include:

4. Credits

Some important sections of the ATV code were written and contributed by David Schlegel, Douglas Finkbeiner, Michael Liu, and Wesley Colley. The FITS I/O, astrometry, and photometry routines used by ATV are part of the IDL Astronomy User's Library, maintained by Wayne Landsman at NASA/GSFC1. ATV also uses a PostScript configuration tool written by Craig Markwardt2. Instructions and complete documentation can be found at the ATV web page:


... Markwardt2

© Copyright 2001 Astronomical Society of the Pacific, 390 Ashton Avenue, San Francisco, California 94112, USA
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