TweakRegStep¶

class romancal.tweakreg.TweakRegStep(name=None, parent=None, config_file=None, _validate_kwds=True, **kws)[source]¶

Bases: RomanStep

TweakRegStep: Image alignment based on catalogs of sources detected in input images.

Create a Step instance.

Parameters:

name (str, optional) – The name of the Step instance. Used in logging messages and in cache filenames. If not provided, one will be generated based on the class name.
parent (Step instance, optional) – The parent step of this step. Used to determine a fully-qualified name for this step, and to determine the mode in which to run this step.
config_file (str or pathlib.Path, optional) – The path to the config file that this step was initialized with. Use to determine relative path names of other config files.
**kws (dict) – Additional parameters to set. These will be set as member variables on the new Step instance.

Attributes Summary

`class_alias`
`reference_file_types`
`spec`

Methods Summary

`do_absolute_alignment`(ref_image, imcats)	Perform absolute alignment of images.
`do_relative_alignment`(imcats)	Perform relative alignment of images.
`get_tweakreg_catalog`(source_catalog, image_model)	Retrieve the tweakreg catalog from source detection.
`process`(input)	This is where real work happens.
`read_catalog`(catalog_name)	Reads a source catalog from a specified file.
`update_catalog_coordinates`(...)	Update the source catalog coordinates using the tweaked WCS.

Attributes Documentation

class_alias = 'tweakreg'¶

reference_file_types: ClassVar = []¶

spec¶

use_custom_catalogs = boolean(default=False) # Use custom user-provided catalogs?
catalog_format = string(default='ascii.ecsv') # Catalog output file format
catfile = string(default='') # Name of the file with a list of custom user-provided catalogs
catalog_path = string(default='') # Catalog output file path
enforce_user_order = boolean(default=False) # Align images in user specified order?
expand_refcat = boolean(default=False) # Expand reference catalog with new sources?
minobj = integer(default=15) # Minimum number of objects acceptable for matching
searchrad = float(default=2.0) # The search radius in arcsec for a match
use2dhist = boolean(default=True) # Use 2d histogram to find initial offset?
separation = float(default=1.0) # Minimum object separation in arcsec
tolerance = float(default=0.7) # Matching tolerance for xyxymatch in arcsec
fitgeometry = option('shift', 'rshift', 'rscale', 'general', default='rshift') # Fitting geometry
nclip = integer(min=0, default=3) # Number of clipping iterations in fit
sigma = float(min=0.0, default=3.0) # Clipping limit in sigma units
abs_refcat = string(default='GAIADR3')  # Absolute reference
# catalog. Options: GAIADR3,GAIADR2,GAIADR1
save_abs_catalog = boolean(default=False)  # Write out used absolute astrometric reference catalog as a separate product
abs_minobj = integer(default=15) # Minimum number of objects acceptable for matching when performing absolute astrometry
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=1.0) # 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')
abs_nclip = integer(min=0, default=3) # Number of clipping iterations in fit when performing absolute astrometry
abs_sigma = float(min=0.0, default=3.0) # Clipping limit in sigma units when performing absolute astrometry
output_use_model = boolean(default=True)  # When saving use `DataModel.meta.filename`
update_source_catalog_coordinates = boolean(default=False) # Update source catalog file with tweaked coordinates?
save_l1_wcs = boolean(default=True)

Methods Documentation

do_absolute_alignment(ref_image, imcats)[source]¶

Perform absolute alignment of images.

This method retrieves a reference image and performs absolute alignment using the specified parameters, including reference WCS information and catalog details. It aligns the provided image catalogs to the absolute reference catalog.

Parameters:

ref_image (DataModel) – The reference image used for alignment, which contains WCS information.
imcats (list) – A list of image catalogs containing source information for alignment.

Return type:

None

do_relative_alignment(imcats)[source]¶

Perform relative alignment of images.

This method performs relative alignment with the specified parameters, including search radius, separation, and fitting geometry.

Parameters:: imcats (list) – A list of image catalogs containing source information for alignment.
Return type:: None

get_tweakreg_catalog(source_catalog, image_model)[source]¶

Retrieve the tweakreg catalog from source detection.

This method checks the source detection metadata for the presence of a tweakreg catalog data or a string with its name. It returns the catalog as a Table object if either is found, or raises an error if neither is available.

Parameters:

source_catalog (object) – The source catalog metadata containing catalog information.
image_model (DataModel) – The image model associated with the source detection.

Returns:

The retrieved tweakreg catalog as a Table object.

Return type:

Table

Raises:

AttributeError – If the required catalog information is missing from the source detection.

process(input)[source]¶: This is where real work happens. Every Step subclass has to override this method. The default behaviour is to raise a NotImplementedError exception.

read_catalog(catalog_name)[source]¶

Reads a source catalog from a specified file.

This function determines the format of the catalog based on the file extension:

“asdf”: uses roman datamodels
“parquet”: uses pyarrow
otherwise: uses astropy Table.

Parameters:: catalog_name (str) – The name of the catalog file to read.
Returns:: The read catalog as a Table object.
Return type:: Table
Raises:: ValueError – If the catalog format is unsupported.

update_catalog_coordinates(tweakreg_catalog_name, tweaked_wcs)[source]¶

Update the source catalog coordinates using the tweaked WCS.

Parameters:

tweakreg_catalog_name (str) – The name of the TweakReg catalog file produced by SourceCatalog.
tweaked_wcs (gwcs.wcs.WCS) – The tweaked World Coordinate System (WCS) object.

Return type:

None