Automates the use of both drizzle and blot by calculating all the necessary parameters, creating the appropriate distortion coefficients tables, and keeping track of all the inputs and outputs.
Generates association tables for user-specified sets of images to be processed by PyDrizzle.
Computes the distortion corrected RA/Dec based on the X/Y pixel position from a distorted image.
All these tasks have both a Python command line interface as well as an IRAF parameter-driven interface suitable for use with PyRAF's graphical EPAR. Pipeline use only requires the name of the input association table or exposure as input while all other parameters can be determined automatically or use conservative default values. This allows the task to be run, in most cases, with only one simple command and almost no parameters compared to the many required parameters for the drizzle or blot tasks themselves.
The task pydrizzle provides the user with the ability to:
These capabilities allow PyDrizzle to maintain all the bookkeeping necessary for performing more advanced processing such as cosmic-ray rejection using the techniques from the Dither Handbook. PyDrizzle can also serve as the basis for a library of functions usable by any Python task for astronomical reductions. The xytosky task demonstrates how the methods from PyDrizzle can be developed into a separate task for use on data from any supported instrument.
A lot of work still needs to be done to expand the range of additional tasks derived from the PyDrizzle methods and classes, such as a skytoxy task, with an emphasis on making them generally applicable to any astronomical dataset. However, the current software still represents a dramatic step forward in the ease of use of advanced image processing, specifically processing provided by the tasks in the STSDAS dither package.
A serious effort to provide documentation for PyDrizzle has been undertaken, starting with built-in help, IRAF-style help files in STSDAS and a user's guide for PyDrizzle. As a starting place, a preliminary draft of the first chapter of a user's guide can be downloaded from the WWW site, with the full version being posted as soon as it gets completed.
Currently, Specview fully supports a variety of FITS file formats:
Specview provides a number of interactive tools to enable the user to explore the internal structure of complex spectroscopic files, such as STIS and IUE echelle data. It provides interactive tools for zooming and panning into the data, and for selecting particular data arrays within a file. There are also interactive tools for browsing the FITS headers, and for customizing the plots, such as a physical units selector, log scaling, a color and plot style editor, and plot annotation. Plots can be sent to a hardcopy device or a file. Most of these features can be accessed from buttons or menus shown in Figure 1.
Specview features a powerful spectral model fitting engine which allows the user to: build spectral models, maintain spectral models using interactive tools, and fit data using non-linear chi-square minimization. Models are built from spectral components selectable from a library. Choices include functions such as blackbody, power laws, recombination continuum, bremsstrahlung, accretion disk, a variety of Gaussian types, Lorentz, Voigt, etc. Components can be edited in a variety of ways, and also be constrained to each other using physical criteria. Users with minimal proficiency in Java coding can add their own functions to the library as well. Models can be saved to disk at any time and brought back later for further use.
A ``quick measurement tool'' is in the works to provide point-and-click functionality to measure spectral line properties without the need to invoke the full power of the model fitting engine. Also in the works is a data processing engine that will provide spectrum arithmetic, splicing, rebinning, and Fourier filtering capabilities.
Specview has been tested under a variety of systems: Solaris, Linux, Windows 98/NT/XP. A MacOS X port will occur in the near future.
The software can be downloaded from the Specview WWW pages.
Fruchter, A. S. & Hook R. N. 2002, PASP, 114, 144