EXTRACTOR, will read data in floating point format. It will also read NDFs that contain BAD pixels.
These will appear as “missing” regions, so any objects that are intersected will be split into
parts.
Since EXTRACTOR uses the AST (SUN/211) library to perform astrometry, it can be used with images
that contain DSS calibrations, as well as FITS-WCS and AST native ones (native SExtractor will only
use images that have FITS-WCS calibrations). The GAIA display tool is a convenient way to add such
astrometrical calibrations.
Two current limitations are that no support is provided for the use of NDF variance arrays (although
these would probably map onto the “weight” image concept of SExtractor) and that the
propagation of the input NDF to the check image is not done (so WCS calibration, for instance, is
lost).
NDF pixel coordinates (i.e. ones that include the NDF origin) can be obtained using the X_PIXEL and
Y_PIXEL parameters.
The SExtractor program has a very large range of processing options. Consequently many of these
options have not been tried extensively in the EXTRACTOR incarnation, so some problems may arise,
when using non-default configurations.
A SExtractor facility that has not been implemented is the piping of catalogues to standard output.
The use of weight and flag images are not supported.
Finally as noted earlier the galaxy fitting parameters are not available.
If you come across any problems with EXTRACTOR please notify Starlink Software Support
(starlink@jiscmail.ac.uk).