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 processing algo-
rithms 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 tak-
ing care of many aspects of astronomical image processing. Users will
want to use only Unix commands to process their data, programmers and
algorithm developers will want to peek into the libraries to implement
their own routines.
All of these procedures are running without user interaction, 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.
Since version 4.2, all FITS read/write functions have been moved away
from eclipse to give birth to a small, efficient and easy-to-use FITS
io library: qfits. eclipse needs and is distributed with qfits
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 subtraction 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 dedi-
cated optimized algorithms for data processing. Some commands have been
written to handle pipeline data processing, they are integrated in the
VLT data flow system as data reduction engine for these modes, as a
complement to on-line MIDAS. Both imaging and spectroscopic modes are
supported for ISAAC.
Naco
NACO is an infrared instument that work with an adaptive optic system.
The data reduction is similar as the one used for ISAAC. Reduction
recipe have been developed with the ISAAC experience and adapted to
this new instrument. Support for the NACO instrument has been present
in eclipse since version 4.0
License
eclipse is covered by the GNU public general license, which makes pos-
sible 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 Corporon 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 preci-
sion pixels internally, i.e. all pixel buffers are float *, which lim-
its the precision to 32 bits in IEEE floating point format for all
pixel operations. This is usually enough for most data reduction proce-
dures, 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 procedure 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