Space Telescope Science Institute
Intro to HST Data Handbooks 8.0 May 2011
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Introduction to the HST Data Handbooks > Chapter 3: Analyzing HST Data > 3.2 Navigating STSDAS

The tasks in STSDAS are far too numerous and complicated to describe comprehensively in this volume. Instead, we will show you where to find the STSDAS tasks appropriate for handling certain jobs. You can refer to online help or the STSDAS User’s Guide for details on how to use these tasks. Some useful online help commands are:
apropos word - searches the online help database for tasks relating to the specified word (see Figure 4.4).
help task - provides detailed descriptions and examples of each task.
help package - lists the tasks in a given package and their functions.
describe task - provides a detailed description of each task.
examples task - provides examples of each task.
STSDAS Structure
STSDAS is structured so that related tasks are grouped together as packages. For example, tasks used in the calibration process can be found in the hst_calib package, and tasks used for image display and plotting can be found in the graphics package. Table 3.1 shows the current STSDAS package structure. The current version of IRAF (v2.15 as of November 2010) and TABLES (v3.13 as of January 2011) must be installed on your system in order to use the latest version of STSDAS. It is always a good idea to make sure you have the most recent versions of the software as they often include important code updates. Newer versions of IRAF, STSDAS, and TABLES are released approximately every 6 months to provide extensively tested updates for support of new instruments or to correct bugs in previous versions. Bug fixes and new versions of this package in the process of being tested can be downloaded as the IRAFX environment from:
These pre-release versions are updated weekly to include new code and bug fixes which have not been extensively tested or verified for accuracy by the Institute. They also require a very different installation procedure and can be installed without root access, but are only provided as binaries for the Mac OSX Leopard and Linux Red Hat Enterprise 4 operating systems.. Please check the following Web site for the latest information:
Table 3.1: STSDAS Version 3.13 Package Structure
Access the HST Guide Star Catalog on CD-ROM.
FITS and GEIS input/output for HST data (images and tables).
HST Science Instrument calibration package.
For Images
Both IRAF and STSDAS contain a large number of tasks that work with HST images. Some of the packages you should investigate are:
images: This IRAF package includes general tasks for copying (imcopy), moving (imrename), deleting (imdelete), displaying (tv), and examining (imexamine) image files. These tasks operate on both the header and data portions of the image. The package also contains a number of general purpose tasks for operations such as image statistics, rotating and magnifying images, and registering and dewarping images.
stsdas.toolbox.imgtools: This package contains tools for working with GEIS images, including tasks for working with masks, and general purpose tasks for working with the pixel data, such as an interactive pixel editor (pixedit), and gcombine for coadding GEIS images. Also of note are the tasks imcalc for performing image arithmetic, and rd2xy and xy2rd for converting between RA, Dec and x,y pixel coordinates. Many of these tasks will also work with single group or waivered FITS format files.
stsdas.toolbox.imgtools.mstools: This package contains tools for working with FITS image files, in particular ACS, NICMOS, STIS, and WFC3 image sets (imsets). Msstatistics, for example, will print statistics on each image set (imset) in an image file. Similarly, msarith can be used for image arithmetic and uses information from the Data Quality (DQ), Error (ERR), and if available, the TIME and SAMP extensions in the calculation.
stsdas.analysis.dither.multiDrizzle: This routine is provided as a “one-touch” interface for performing all the tasks necessary for registering dithered HST images, performing cosmic ray rejection, removing geometric distortion and performing the final image combination using “drizzle”.
We are currently developing a replacement for MultiDrizzle which will rely on an extended image header for all the astrometric and distortion information used to geometrically correct and align the images. This new task will be announced as soon as a version has been successfully tested with data from the current imaging instruments on HST.
stsdas.analysis: This package contains general tasks for image analysis, such as Fourier analysis (fourier), dithering (dither), and fitting.
For Tables
Several of the analysis packages in STSDAS, including calibration pipeline tasks, create output files in STSDAS table format (which is a binary row-column format) or in FITS binary table format. (ASCII-format tables are supported, but only for input.) The STSDAS User’s Guide describes the STSDAS table format in detail. Tasks in the ttools package or in the external tables package can be used to read, edit, create, and manipulate tables. For example:
tread displays a table, allowing you to move through it with the arrow keys
tprint displays a table
tcopy copies tables
tedit allows you to edit a table
Many other tasks in ttools perform a variety of other functions. See the online help for details.

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