A tool to prepare astronomical observations



TkParal is an X Window interface for the Paral program of the former Radio Continuum Group of the Max-Planck-Institut für Radioastronomie, Bonn. Paral/TkParal is a convenient tool to plan observing runs at various telescopes. Based on source position and observatory coordinates it calculates azimuth, elevation, parallactic angle, rise and set times and some more parameters.

While many people prefer programs like Astro or XEphem to get information of this kind, I always preferred Paral because it calculates azimuth and parallactic angle as well, and the first derivation of all numbers. Thus you know how a source will be oriented in the sky, and how fast this orientation will change - both parameters which are important to plan e.g. On-The-Fly mapping observations.

One disadvantage of Paral was its very own format for input parameters, and its low tolerance for input errors. TkParal, the X11 interface for Paral, can help, since it detects most possible input errors before sending the parameters to Paral itself. In addition, it provides a list of often used observatories and their coordinates, as well as the possibility to select a source from a catalog.


See a screenshot of TkParal at work.


The code and documentation of TkParal are copyrighted by the author. However, the program is freely available for non-commercial use, and you may even change the code to adjust it to your personal needs.

The software is provided "as is". No warranty is made for the usefulness of this package, and the author accepts no responsibility for any damage which may result from the use or mis-use of this package.

The Paral program © 1984 H. Andernach and the Radio Continuum Group of the Max-Planck-Institut für Radioastronomie, Bonn (Germany).
Many subroutines © 1971-1981 C.G. Haslam and the Radio Continuum Group of the Max-Planck-Institut für Radioastronomie, Bonn (Germany).


The current version of TkParal is 1.41


The current web address for TkParal is Get the code by a http request from this site: tkparal.tar.gz. This is a gzipped tar archive. Uncompress and untar the file to create a subdirectory called "TkParal". In the subdirectory TkParal/main, type "make" to compile the main Paral program. Second, type "make clean" to delete unneeded object files, and third edit the Tcl/Tk script tkparal to reflect the location of the installation directory and the default directory where your source catalogs reside. Then copy tkparal to a directory which is in your $PATH environment variable.

You will further need the following software:

Since TkParal is just a script, it should run on any platform where Tcl/Tk is installed. I developed it using Tcl/Tk release 8.3.0. The compilation of the underlying Paral program should also be straightforward. Please adjust the makefile to your system, if necessary.
The package has been successfully installed and tested on Linux (SuSE, Fedora) and Solaris (SunOS 5.6 and higher).


If you have questions about TkParal, please send them to Michael Dumke, preferably by e-mail to mdumke(at) If you have a problem with the installation, please include information about your operating system version, Fortran compiler, and the version of Tcl/Tk you are using.

© 2000 - 2023 Michael Dumke. Any view or statement made on this page is not part of an official standpoint of PUC, MPIfR, or APEX. Last modified: 29 October 2023.