autowisp.astrometry.astrometry module

Class Inheritance Diagram

Fit for a transformation between sky and image coordinates.

class autowisp.astrometry.astrometry.TempAstrometryFiles(file_types=('sources', 'corr', 'config'))

Bases: object

Context manager for the temporary files needed for astrometry.

__enter__()

Return the filenames of the temporary files.

__exit__(*ignored_args, **ignored_kwargs)

Close and delete the temporary files.

__init__(file_types=('sources', 'corr', 'config'))

Create all required temporary files.

autowisp.astrometry.astrometry._ansvr_bash()

Return the ANSVR cygwin bash path on Windows if installed, else None.

ANSVR (https://adgsoftware.com/ansvr/) is how solve-field is provided on Windows; its solve-field is a cygwin binary invoked through this bash, so it never appears on the Windows PATH.

autowisp.astrometry.astrometry.create_config_file(config_fname, fov_range, anet_indices)

Create configuration file set up to solve images FOV in given range.

autowisp.astrometry.astrometry.create_sources_file(xy_extracted, sources_fname)

Create a FITS BinTable file with the given name containing the extracted sources.

Returns: an array containing x-y extracted sources

autowisp.astrometry.astrometry.estimate_transformation(*, config, **initial_corr_kwarg)

Attempt to estimate the sky-to-frame transformation for given DR file.

autowisp.astrometry.astrometry.estimate_transformation_from_corr(initial_corr, tweak_order, astrometry_order, x_cent, y_cent)

Estimate the transformation from astrometry.net correspondence file.

Parameters:

• initial_corr (structured numpy array) – The correspondence file containing field_x, field_y, index_ra, and index_dec

• tweak_order (int) – The order of the astrometry.net transformation

• astrometry_order (int) – The order of the transformation that will be fit. Fills terms of higher order than tweak_order with zeros.

• x_cent (float) – The x pixel coordinate of the frame center (used as the reference point for the gnomonic projection).

• y_cent (float) – The y pixel coordinate of the frame center (used as the reference point for the gnomonic projection).

Returns:

ra_cent: The RA corresponding to (x_cent, y_cent) coordinate in the

image.

dec_cent: The Dec corresponding to (x_cent, y_cent) coordinate in

the image.

trans_x:

Estimate of the transformation coefficients for x(xi, eta)

trans_y:

Estimate of the transformation coefficients for y(xi, eta)

Return type:

dict

autowisp.astrometry.astrometry.find_ra_dec(xieta_guess, trans_x, trans_y, radec_cent, frame_x, frame_y)

Find the RA and Dec corresponding to given pixel coordinates in the frame.

Solves for the gnomonic-projection coordinates (xi, eta) that map to the given frame pixel position via the polynomial astrometric transformation, then converts (xi, eta) to sky coordinates via inverse gnomonic projection.

Parameters:

• xieta_guess (numpy array) – Starting point for the solver trying to find (xi, eta) that map to the given coordinates.

• trans_x (numpy array) – Polynomial transformation coefficients for x, shape (n_terms, 1).

• trans_y (numpy array) – Polynomial transformation coefficients for y, shape (n_terms, 1).

• radec_cent (dict) – The RA and Dec of the center of the gnomonic projection defining (xi, eta).

• frame_x (float) – x coordinate for which to find RA, Dec.

• frame_y (float) – y coordinate for which to find RA, Dec.

Returns:

A dictionary with keys 'RA' and 'Dec' (both float),

giving the sky coordinates corresponding to the given frame position.

Return type:

dict

autowisp.astrometry.astrometry.get_initial_corr(*, dr_file, xy_extracted, config, header=None, web_lock=None)

Attempt to estimate the sky-to-frame transformation for given DR file.

autowisp.astrometry.astrometry.get_initial_corr_local(header, xy_extracted, tweak_order_range, fov_range, anet_indices)

Get inital extracted to catalog source match using solve-field.

autowisp.astrometry.astrometry.get_initial_corr_web(header, xy_extracted, tweak_order_range, fov_range, api_key)

Get initial extracted-to-catalog match via web astrometry.net.

autowisp.astrometry.astrometry.local_solver_available()

Whether a local solve-field can be invoked (native or via ANSVR).

autowisp.astrometry.astrometry.refine_transformation(*, astrometry_order, max_srcmatch_distance, max_iterations, trans_threshold, trans_x, trans_y, ra_cent, dec_cent, x_frame, y_frame, xy_extracted, catalog, min_source_safety_factor=5.0)

Iterate the process until we get a transformation that its difference from the previous one is less than a threshold

Parameters:

• astrometry_order (int) – The order of the transformation to fit

• max_srcmatch_distance (float) – The upper bound distance in the KD tree

• trans_threshold (float) – The threshold for the difference of two consecutive transformations

• trans_x (numpy array) – Initial estimate for the x transformation matrix

• trans_y (numpy array) – Initial estimate for the y transformation matrix

• ra_cent (float) – Initial estimate for the RA of the center of the frame

• dec_cent (float) – Initial estimate for the Dec of the center of the frame

• x_frame (float) – length of the frame in pixels

• y_frame (float) – width of the frame in pixels

• xy_extracted (structured numpy array) – x and y of the extracted sources of the frame

• catalog (pandas.DataFrame) – The catalog of sources to match to

Returns:

the coefficients of the x(xi, eta) transformation

trans_y(2D numpy array):

the coefficients of the y(xi, eta) transformation

cat_extracted_corr(structured numpy array):

the catalogs extracted correspondence indexes

res_rms(float): the residual

ratio(float): the ratio of matched to unmatched

ra_cent(float): the new RA center array

dec_cent(float): the new Dec center array

Return type:

trans_x(2D numpy array)

autowisp.astrometry.astrometry.transformation_matrix(astrometry_order, xi, eta)

Constructs the transformation matrix for a given astrometry order.

Parameters:

• astrometry_order (int) – The order of the transformation to fit

• xi (numpy.ndarray) – from projected coordinates

• eta (numpy.ndarray) – from projected coordinates

Returns:

transformation matrix

Return type:

trans_matrix(numpy.ndarray)

Notes

Ex: for astrometry_order 2: 1, xi, eta, xi^2, xi*eta, eta^2