2008-05-21

Astronomical image processing guide (Intro)

From time to time, I'm thinking about the most useful way to process of an astronomical image data. An use of wide-known software package utilities like Gaia, ds9, IRAF may be better or worse in comparison of a direct coding of a self-made routine? Both approaches has its own advantages and disadvantages so, I think, there is no an universal way to process its. For example, a lot of work can be done inside IRAF's (http://iraf.noao.edu/) environment, but sometimes may be faster and more suitable of coding of an own utility. Both approaches may be possible useful and important especially for a particular processing. Also, I thinks the develop of any own routine may be much, much better and simpler then use of prepared ones. While there is a lot of documents describing of various software packages, the processing in a computer language is described poorly. That's why I'm starting write this guide.

The basic operation to work with data is data file handling. A FITS format (http://heasarc.gsfc.nasa.gov/docs/heasarc/fits.html) is a wide-used format to storing of an astronomical data including both an images and a data tables. A general structure of FITS files may be really very complicated. Fortunately, W. Pence and etc. made the cFITSIO library to provide of a standard way to create, open and modify of any FITS files. The library offers interfaces for C and Fortran languages. There is also a lot of wrappers to others (Perl, Python, C++, ..). I'll use of Fortran (fortran 90/95/2003 dialect) in this guide to create a simple code but the change to C (for example) is straightforward.

A computer library (like cfitsio) is a file with a special structure which includes a set of (useful) functions. The file is usually created by compiling of a computer language (cfitsio is in C) to a machine-specific code.

How to install an environment to open FITS files?

1. Use of your package system and install gfortran (Fortran compiler).
2. Use of your package system and install cfitsio.

ad 1). The gfortran is included in most modern Linuxes. Its is possible to use also Intel's ifort (apparently faster). Solaris offers f90/f95. The GNU g95 provides binaries for other systems (BSD's, Mac OSX, ..).

ad 2) Many modern distributions (Debian, Ubuntu, Fedora..) offers cfitsio as a package. If your doesn't, download directly tarball. Move it to /tmp and execute:
host:/tmp$ tar zxf cfitsio-x.y.z.tar.gz
host:/tmp$ cd cfistio-x.y.z
host:/tmp$ ./configure # check output
host:/tmp$ make # compile
host:/tmp$ su # switch to root account
host:/tmp$ make install # install to /usr/local

To install it in an another place use --prefix parameter for configure (./configure --help). To uninstall it, type (as root) make uninstall. A successful installation is indicated by presence of drvrsmem.h,fitsio.h, fitsio2.h and longnam.h in /usr/local/include and libcfitsio.a in /usr/local/lib.
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