Obit - Astronomy Software for the Recently Deceased

Overview

Obit is a Unix software environment with a limited set of developed applications. It is an object--oriented set of class and utility libraries allowing access to multiple disk--resident data formats. In particular, access to either AIPS disk data or FITS files. A number of low level applications are inplemented such as imaging and deconvolving interferometer or OTF data, High-level applications may be either compiled c programs or python scripts; most of the high-level operations have bindings to python.

Obit Components

• Obit

  This is the basic Obit package containing astronomical images and radio interferometry data and applications. A gzipped tarball is available here

• ObitSD

  Ths is a single dish "On-the-fly" (OTF) imaging addon to Obit. Only FITS format files are supported. A gzipped tarball is available here

• ObitView

  This is a Unix/X-Windows program that serves as an Image display server. Communications is through the xmlrpc protocol but only a local implementation is currently supported. It is currently usable by Obit and ObitSD to display images and interactively select CLEAN windows. ObitView can browse and display FITS images or local AIPS images can be displayed if requested via the xmlrpc interface. A gzipped tarball is available here

• ParselTongue

  ParselTongue is a python-based scripting and interactive command line interface to astronomical data processing packages. ParselTongue can execute Obit tasks (compiled programs) and use the Obit python interface in a script. ParselTongue is an EU funded component of RadioNet and is being developed by the Joint Institute for VLBI in Europe (JIVE). ParselTongue documentation is available here

Installing the Software

• python

  Python is used as the scripting and interactive interface to Obit. Python 2.3 or later is needed. Get python here.

• cfitsio

  Basic FITS I/O package, used for all access to FITS files. If not found, a stubbed version will be used but all access to FITS files will fail. Available here. You'll need to create include and lib directories and put the header files and library there.

• glib

  The gnu library for large scale software in ansci c. Available here.

• FFTW

  Fast Fourier Transform. Available here. Note: FFTW MUST be installed with the configure option --enable-float to be used by Obit.

• gsl

  GNU Scientific Library. Available here.

• pgplot

  Fortran based graphics package. This is not widely used in Obit and if not found in the installation procedures, calls to pgplot routines are stubbed. Available here.

• xmlrpl

  Interprocess communications software used to communicate between c software and ObitView. If this is not found by the installation software, a stubbed version will be used but the interprocess communication ability is lost. Available here. Build and installation procedures may fail prior to completion but this doesn't seem to matter.

• www

  Used by xmlrpl. Available here. An earlier but defective version is widespread. You may need in get a recent version and install it separately. Build and installation procedures may fail prior to completion but this doesn't seem to matter. There are a LARGE number of libraries involved. There may be a problem with libwwwzip.a, I had to copy this from an older installation.

• zlib

  Gzip compressed file IO used by ObitView. Available here.

• motif

  ObitView uses the Motif library. A freebee plug-compatible replacement is LessTif, available here.

Obit software comes with a configuration procedure; in the simplest case, installation from a tarball consists of:
% gtar xzvf Obit.tgz
% ./configure
% make
This will install Obit in directory Obit of the current directory.

If you've installed third party software in a nonstandard location (or to tell configure where you've installed the basic Obit) you'll need to tell configure, e.g.:
% configure --with-obit=$OBIT --with-pgplot=$HOME/opt/pgplot \
--with-cfitsio=$HOME/opt/cfitsio --with-fftw=$HOME/opt/fftw \
--with-xmlrpc=$HOME/opt/xmlrpc --with-www=$HOME/opt/WWW \
CC=/usr/bin/gcc

To use Python, you'll need to set the environment variable PYTHONPATH to include the Obit/python (and ObitSD/python if it is to be accessable). Ecample for tcsh:
setenv PYTHONPATH "$OBITSD/python":"$OBIT/python" where $OBIT is set to the base address of the Obit software and $OBITSD to the base address of the ObitSD software (if needed).

Running Obit Software

Some setup is needed for Obit python scripts, there are examples in the python/script*.py files. Online help is available for the Obit python classes through the python Help facility.

ObitView must be started independently and can be used as an independent FITS image browser. FITS files can be downloaded from the internet by giving a full URL. If ObitView has been built using xmlrpc only one version is allowed to run at a time.

ObitView can be told to display AIPS images as seen in the following python code fragment which lists the AIPS files in directory /DATA/LUSUS_1/ and then selects one and has ObitView display it.

import Obit, OSystem, OErr, AIPSDir, Image, ODisplay

# Init Obit - defining AIPS directory
err=OErr.OErr()
ObitSys=OSystem.OSystem ("Display", 1, 100, 1, ["/DATA/LUSUS_1/"], 1, ["."], 1, 0, err)
OErr.printErrMsg(err, "Error with Obit startup")

# list AIPS directory
disk=1
AIPSDir.PListDir(disk, err)

# Display image in catalog slot 4
a=Image.newPACNO(1,4,True,err) # create image object
d=ODisplay.ODisplay("ObitView","ObitView",err) # create display client
ODisplay.PImage(d,a,err) # display

# Shutdown Obit
OErr.printErr(err)
del ObitSys