data can be manipulated with several different software packages. In this section we introduce a few of the software language options.
is an IRAF
package developed by STScI for the reduction and analysis of HST
data. The package contains tasks
that perform a wide range of functions supporting the entire data analysis process, from reading tapes, through reduction and analysis, to producing final plots and images. Sections 3.2 through 3.7 introduce the basics of STSDAS
, illustrating how to display HST
data, presenting some simple data manipulations, and pointing you towards more sophisticated tasks.
is layered on top of the Image Reduction and Analysis Facility
software developed at the National Optical Astronomy Observatory (NOAO). Any task in IRAF
can be used in STSDAS
, and the software is portable across a number of platforms and operating systems. To exploit the power of STSDAS
, you need to know the basics of IRAF
. If you are not already familiar with IRAF
, consult the IRAF
Primer in Chapter 4
before reading further.
is a command language for IRAF
that is based on Python. It has a number of advantages over the IRAF
CL. Most importantly, with few exceptions, it allows use of exactly the same syntax as the IRAF
CL. Some of the advantages that it provides are:
is so highly compatible with the IRAF
CL, virtually all of the examples shown in this handbook will work the same for PyRAF
. Minor differences include the user prompt and the graphics windows appearance.
Python is used for astronomical data reduction applications. It is a freely available,
general-purpose, dynamically-typed interactive language that provides modules for scientific programming and is used for astronomical data reduction application. These modules include:
Python is a very powerful language that is well suited to writing programs to solve
many needs beside scientific analysis. Tools are available to read (but currently not write) GEIS files.
Python can make use of PyRAF
to allow access to IRAF
tasks. Tutorials are available which illustrate the use of Python for interactive data analysis in astronomy (in much the same style as is now popular with IDL). The initial focus of these tutorials is the use of interactive tasks for the novice user. The more advanced tutorials focus on teaching the details of Python programming. The tutorials can be downloaded from:
STScI is developing most of its new calibration and data analysis software in
Python. More information on the use of Python to analyze HST
data can be obtained from:
IDL is an array-based, interactive programming language that provides many
numerical analysis and visualization tools. It is typically much easier to develop new analysis and visualization applications and utilities in IDL than in Fortran or C. As a result, it is very popular in the astronomical community with many astronomers using it for their analysis of HST
It can be obtained from ITT Visual Information Solutions
), for a fee. Libraries for reading HST
data are part of the freely available ASTRON library (http://idlastro.gsfc.nasa.gov
) which has links to other IDL astronomy libraries.
This library does not support GEIS format directly so users will need to use the
waivered FITS format obtained from the archive and manually extract the needed information.