diff --git a/CHANGES.rst b/CHANGES.rst index 74a1a38f0a..b579c289db 100644 --- a/CHANGES.rst +++ b/CHANGES.rst @@ -23,7 +23,7 @@ associations and dither pointing, ``MOSTILNO`` and ``DITHPTIN``. [#8410] dark_current ------------- +------------ - Add log info message when specifying an average_dark_current for noise calculations. [#8425] @@ -33,7 +33,7 @@ documentation - Added docs for the NIRSpec MSA metadata file to the data products area of RTD. [#8399] - + - Added documentation for multiprocessing. [#8408] extract_1d @@ -104,6 +104,9 @@ tweakreg - Improved how a image group name is determined. [#8426] +- Changed default settings for ``abs_separation`` parameter for the ``tweakreg`` + step to have a value compatible with the ``abs_tolerance`` parameter. [#8445] + 1.14.0 (2024-03-29) =================== diff --git a/docs/jwst/tweakreg/README.rst b/docs/jwst/tweakreg/README.rst index ac0c0588fb..30e39ba0b5 100644 --- a/docs/jwst/tweakreg/README.rst +++ b/docs/jwst/tweakreg/README.rst @@ -21,8 +21,8 @@ format automatically recognized by :py:meth:`~astropy.table.Table.read`. When the ``meta.tweakreg_catalog`` attribute of input data models is `None` or an empty string, then the ``tweakreg`` step will attempt to detect sources in the input images. Stars are detected in the image with one of the following source -detection algorithms: ``photutils.detection.DAOStarFinder`` (default), -``photutils.detection.IRAFStarFinder``, or ``photutils.segmentation.SourceFinder`` +detection algorithms: ``photutils.detection.DAOStarFinder`` (default), +``photutils.detection.IRAFStarFinder``, or ``photutils.segmentation.SourceFinder`` in conjunction with ``photutils.segmentation.SourceCatalog``. DAOStarFinder is an implementation of the `DAOFIND`_ algorithm @@ -38,26 +38,26 @@ specified. IRAFStarFinder is a Python implementation of the IRAF star finding algorithm, which also calculates the objects' centroids, roundness, and sharpness. However, IRAFStarFinder uses image moments -instead of 1-D Gaussian fits to projected light distributions like +instead of 1-D Gaussian fits to projected light distributions like DAOStarFinder. SourceFinder implements a segmentation algorithm that identifies -sources in an image based on a number of connected pixels above a -specified threshold value. The sources are deblended using a -combination of multi-thresholding and watershed segmentation. +sources in an image based on a number of connected pixels above a +specified threshold value. The sources are deblended using a +combination of multi-thresholding and watershed segmentation. SourceCatalog finds the centroids of these sources, which are used -as the retrieved star positions. +as the retrieved star positions. .. warning:: - It has been shown (`STScI Technical Report JWST-STScI-008116, SM-12 - `_) + It has been shown (`STScI Technical Report JWST-STScI-008116, SM-12 + `_) that for undersampled PSFs, e.g. for short-wavelength NIRISS imaging data, ``DAOStarFinder`` gives bad results no matter the input parameters due to its use of 1-D Gaussian fits. ``IRAFStarFinder`` or ``SourceFinder`` should be used instead. -.. note:: - ``SourceFinder`` is likely to detect non-stellar sources +.. note:: + ``SourceFinder`` is likely to detect non-stellar sources such as galaxies because sources are not assumed to be point-source-like. This may lead to mismatches between the derived source catalog and the reference catalog during the @@ -254,7 +254,7 @@ The ``tweakreg`` step has the following optional arguments: **Additional source finding parameters for segmentation:** -* ``npixels``: An `int` value indicating the minimum number of +* ``npixels``: An `int` value indicating the minimum number of connected pixels that comprises a segment (Default=10) * ``connectivity``: An `int` value indicating the connectivity defining the @@ -280,7 +280,7 @@ The ``tweakreg`` step has the following optional arguments: Allowed values: `'correct'`, `'mask'`, `'none'`. (Default= `'correct'`) * ``kron_params``: A tuple of `float` values indicating the - parameters defining Kron aperture. If None, + parameters defining Kron aperture. If None, the parameters `(2.5, 1.4, 0.0)` are used. (Default=None) **Optimize alignment order:** @@ -374,9 +374,7 @@ Parameters used for absolute astrometry to a reference catalog. Otherwise the initial guess for the offsets will be set to zero (Default=True) -* ``abs_separation``: Minimum object separation in arcsec. It is recommended - that a value smaller than ``separation`` be used for this parameter - (e.g. 10 times smaller) (Default=0.1) +* ``abs_separation``: Minimum object separation in arcsec. (Default=1.0) * ``abs_tolerance``: Matching tolerance for ``xyxymatch`` in arcsec. (Default=0.7) diff --git a/jwst/tweakreg/tweakreg_step.py b/jwst/tweakreg/tweakreg_step.py index bddb2c1ff5..cb86e69054 100644 --- a/jwst/tweakreg/tweakreg_step.py +++ b/jwst/tweakreg/tweakreg_step.py @@ -97,7 +97,7 @@ class TweakRegStep(Step): abs_searchrad = float(default=6.0) # The search radius in arcsec for a match when performing absolute astrometry # We encourage setting this parameter to True. Otherwise, xoffset and yoffset will be set to zero. abs_use2dhist = boolean(default=True) # Use 2D histogram to find initial offset when performing absolute astrometry? - abs_separation = float(default=0.1) # Minimum object separation in arcsec when performing absolute astrometry + abs_separation = float(default=1) # Minimum object separation in arcsec when performing absolute astrometry abs_tolerance = float(default=0.7) # Matching tolerance for xyxymatch in arcsec when performing absolute astrometry # Fitting geometry when performing absolute astrometry abs_fitgeometry = option('shift', 'rshift', 'rscale', 'general', default='rshift')