Module: wcs_utils

A collection of utility functions for working with WCS in KBMOD.

kbmod.wcs_utils.append_wcs_to_hdu_header(wcs, header)

Append the WCS fields to an existing HDU header.

Parameters:

wcsastropy.wcs.WCS or dict

The WCS to use or a dictionary with the necessary information.

headerastropy.io.fits.Header

The header to which to append the data.

kbmod.wcs_utils.calc_ecliptic_angle(wcs, center_pixel=(1000, 2000), step=12)

Projects an unit-vector parallel with the ecliptic onto the image and calculates the angle of the projected unit-vector in the pixel space.

Parameters:

wcsastropy.wcs.WCS

World Coordinate System object.

center_pixeltuple, array-like

Pixel coordinates of image center.

stepfloat or int

Size of step, in arcseconds, used to find the pixel coordinates of the second pixel in the image parallel to the ecliptic.

Returns:

suggested_anglefloat

Angle the projected unit-vector parallel to the eclipticc closes with the image axes. Used to transform the specified search angles, with respect to the ecliptic, to search angles within the image.

Notes

It is not neccessary to calculate this angle for each image in an image set if they have all been warped to a common WCS.

kbmod.wcs_utils.deserialize_wcs(wcs_str)

Convert a JSON string into a WCS object.

Parameters:

wcs_strstr

The serialized WCS.

Returns:

wcsastropy.wcs.WCS or None

The resulting WCS or None if no data is provided.

kbmod.wcs_utils.extract_wcs_from_hdu_header(header)

Read an WCS from the an HDU header and do basic validity checking.

Parameters:

headerastropy.io.fits.Header

The header from which to read the data.

Returns:

curr_wcsastropy.wcs.WCS

The WCS or None if it does not exist.

kbmod.wcs_utils.make_fake_wcs(center_ra, center_dec, height, width, deg_per_pixel=None)

Create a fake WCS given basic information. This is not a realistic WCS in terms of astronomy, but can provide a place holder for many tests.

Parameters:

center_rafloat

The center of the pointing in RA (degrees)

center_devfloat

The center of the pointing in DEC (degrees)

heightint

The image height (pixels).

widthint

The image width (pixels).

deg_per_pixelfloat, optional

The angular resolution of a pixel (degrees).

Returns:

resultastropy.wcs.WCS

The resulting WCS.

kbmod.wcs_utils.serialize_wcs(wcs)

Convert a WCS into a JSON string.

Parameters:

wcsastropy.wcs.WCS or None

The WCS to convert.

Returns:

wcs_strstr

The serialized WCS. Returns an empty string if wcs is None.

kbmod.wcs_utils.wcs_fits_equal(wcs_a, wcs_b)

Test if two WCS objects are equal at the level they would be written to FITS headers. Treats a pair of None values as equal.

Parameters:

wcs_aastropy.wcs.WCS

The WCS of the first object.

wcs_bastropy.wcs.WCS

The WCS of the second object.