Name
eclipse - (ESO C Library for an Image Processing Software
Environment)
Description
eclipse is a general FITS image processing library written
in ANSI C.
History
Initially written for Adonis, eclipse has since grown to a
general multi-purpose FITS handling utility. It has been
reported to be used on many telescope workstations and
observatories.
Today, eclipse is used in ESO to implement fast image pro-
cessing algorithms for the VLT infrared instruments.
Overview
eclipse offers an open environment for image processing
algorithm developments. At the highest level, only Unix
commands are offered, giving users the possibility to call
the algorithms embedded into the library. One level below
is a library of several hundred functions taking care of
many aspects of astronomical image processing. Users will
want to use only Unix commands to process their data, pro-
grammers and algorithm developers will want to peek into
the libraries to implement their own routines.
All of these procedures are running without user interac-
tion, which is typical of a pipeline, number-crunching
approach.
Notice that a link to off-line data processing softwares
is essential. eclipse does not provide any complex post-
processing algorithm such as deconvolution, nor does it
contain any image or data displayer. Global data analyzers
such as MIDAS provide the full range of functionalities
needed for evolved post-processing and analyses; eclipse
is to be used as a pre-processor, a signal processing
engine.
Adonis
A set of scripts and Unix commands has been especially
designed to take care of most basic data reductions for
Adonis. This has been set up during August 1996 in la
Silla, with h.PP from observers, telescope and Adonis
team.
The following set of operations has been automated:
flat-field creation
bad pixel detection
sky extraction from data cube, averaging, and subtrac-
tion from
object frames
average of the result
There is a preparation phase, during which the observer
has to identify their files according to their logbook,
and sort them out, preferrably in separate directories. It
is then possible to design quickly a Unix script to launch
a unique reduction command on all directories, and get
cleaned data in a very short time.
Since version 2.0, a new set of commands is available for
Adonis Fabry-Perot mode. This work has been validated in
Summer 1997 in la Silla, by Christian Drouet d'Aubigny,
with h.PP from Patrice Corporon and David le Mignant.
Sofi/Isaac
SOFI and ISAAC are two ESO infrared instruments. SOFI is
working on the NTT in la Silla, ISAAC is installed on the
UT1 telescope of the VLT. These instruments are mostly
used in jitter mode, which requires dedicated optimized
algorithms for data processing. Some commands have been
written to handle pipeline data processing, they are inte-
grated in the VLT data flow system as data reduction
engine for these modes, as a complement to on-line MIDAS.
License
eclipse is covered by the GNU public general license,
which makes possible to distribute it on the World Wide
Web. It should be included in future MIDAS distributions
as a contribution for pipeline processing.
I would like to thank all people participating in the High
Resolution Data Reduction Working Group for their kind
h.PP and patience in detailing the secrets of Infra-red
data processing
Special thanks to our friends in la Silla, Patrice Cor-
poron and David le Mignant, for their invaluable h.PP.
Most eclipse documentation is available on-line on the ESO
server at the following address:
http://www.eso.org/eclipse
Internal Pixel Representation
A note about the internal pixel representation:
The convention in use throughout eclipse is to work with
single precision pixels internally, i.e. all pixel buffers
are float *, which limits the precision to 32 bits in IEEE
floating point format for all pixel operations. This is
usually enough for most data reduction procedures, and
gains time in terms of memory use.
You may want however to work with double precision pixels,
to increase computation accuracy. Know that the memory use
in much more intensive in this case, the most probable
case being that all cubes will be swapped to disk for any
pixel operation involving several planes of a cube, the
amount of time used for the same operation being more than
twice the one needed with single-precision pixels: disk
accesses are usually a factor 1000 slower than memory
accesses.
Since version 2.1, it is possible to work with pixels
stored as double precision numbers. The FITS interfaces
have been upgraded to allow input and output in FITS -64
IEEE double format, and the internal pixel representation
may be double, on user request.
This change from single to double precision is not dynamic
but can only be requested at compilation time. The proce-
dure to follow to compile eclipse with double precision
pixels is described in the INSTALL file.
Availability
eclipse is distributed on the WWW under the following URL:
http://www.eso.org/eclipse
See Also
eclipse-commands