ImageSolver

class ctapointing.imagesolver.ImageSolver(**kwargs: Any)

Bases: Component

ImageSolver class.

Hosts algorithms to solve a given image, i.e. determine the position of each individual pixel in sky (RADec) coordinates. Needs a reasonably well-known pointing position for the image. On the basis of this pointing, catalog stars are selected and matched with image spots using quad matching. The matching algorithm of the astroalign package is used.

Attributes Summary

`matching_distance`	maximum distance for quad matching in L2/L1 L0/L1 plane
`matching_radius`	distance in pixels within which a star is matched to a spot in the field matching
`max_magnitude`	maximum magnitude of stars for catalog search
`max_num_spots`	maximum number of image spots used for matching
`max_num_stars`	maximum number of stars used for matching
`max_pointing_deviation`	assumed maximum angular deviation (in degrees) between true and nominalpointing position and/or pointing camera optical axisand true telescope pointing
`min_camera_shadow`	assumed minimum FoV side length (in degrees) blocked by an(assumed square) science camera in the inner part of the image
`min_magnitude`	minimum magnitude of stars for catalog search
`name`	name of ImageSolver
`scale_tolerance`	allowed deviation in true vs.
`uuid`	UUID of ImageSolver

Methods Summary

`from_config`(**kwargs)	Read an ImageSolver configuration from either configuration file or database.
`process`(spotlist, exposure[, ...])	Solve the image given an exposure object.

Attributes Documentation

matching_distance: maximum distance for quad matching in L2/L1 L0/L1 plane

matching_radius: distance in pixels within which a star is matched to a spot in the field matching

max_magnitude: maximum magnitude of stars for catalog search

max_num_spots: maximum number of image spots used for matching

max_num_stars: maximum number of stars used for matching

max_pointing_deviation: assumed maximum angular deviation (in degrees) between true and nominalpointing position and/or pointing camera optical axisand true telescope pointing

min_camera_shadow: assumed minimum FoV side length (in degrees) blocked by an(assumed square) science camera in the inner part of the image

min_magnitude: minimum magnitude of stars for catalog search

name: name of ImageSolver

scale_tolerance: allowed deviation in true vs. nominal focal length of camera

uuid: UUID of ImageSolver

Methods Documentation

classmethod from_config(**kwargs)

Read an ImageSolver configuration from either configuration file or database. Either the path of a configuration file (‘input_url’) or a database collection (‘collection’) must be provided.

Parameters:

input_url (str or Path) – path of the configuration file.
name (str) – name of the ImageSolver (as in ImageSolver.name). When loading the configuration from file, can be set to check that the configuration with the correct name is loaded. When loading from database, is used to identify the correct database record.
uuid (str) – UUID of the camera (as in ImageSolver.uuid). When loading the configuration from file, can be set to check that the configuration with the correct UUID is loaded. When loading from database, is used to identify the correct database record.
collection (str) – name of the database collection from which configuration is read
database (str) – name of the database in which the collection is stored

Returns:

extractor

Return type:

SpotExtractor object

process(spotlist, exposure, estimated_pointing=None, fov_radius=None, image_solution=None)

Solve the image given an exposure object.

Parameters:

spotlist (SpotList) – List of pixel coordinates of extracted spots
exposure (Exposure) – Exposure object. Should be removed at some point.
estimated_pointing (SkyCoord[RADec]) – guess of the optical axis pointing of the telescope. If None, try exposure.nominal_telescope_pointing
fov_radius (Angle or None) – radius of the field of view (for star matching) If set to None, estimated FoV from camera parameters
image_solution (ctapointing.imagesolver.ImageSolution) – object that is to be updated by the results of the image solving process. If None, new ImageSolution object is created and returned by this method.

Return type:

Tuple of Registration object and best-match Quad object

classmethod from_config(**kwargs)

Read an ImageSolver configuration from either configuration file or database. Either the path of a configuration file (‘input_url’) or a database collection (‘collection’) must be provided.

Parameters:

input_url (str or Path) – path of the configuration file.
name (str) – name of the ImageSolver (as in ImageSolver.name). When loading the configuration from file, can be set to check that the configuration with the correct name is loaded. When loading from database, is used to identify the correct database record.
uuid (str) – UUID of the camera (as in ImageSolver.uuid). When loading the configuration from file, can be set to check that the configuration with the correct UUID is loaded. When loading from database, is used to identify the correct database record.
collection (str) – name of the database collection from which configuration is read
database (str) – name of the database in which the collection is stored

Returns:

extractor

Return type:

SpotExtractor object

matching_distance: maximum distance for quad matching in L2/L1 L0/L1 plane

matching_radius: distance in pixels within which a star is matched to a spot in the field matching

max_magnitude: maximum magnitude of stars for catalog search

max_num_spots: maximum number of image spots used for matching

max_num_stars: maximum number of stars used for matching

max_pointing_deviation: assumed maximum angular deviation (in degrees) between true and nominalpointing position and/or pointing camera optical axisand true telescope pointing

min_camera_shadow: assumed minimum FoV side length (in degrees) blocked by an(assumed square) science camera in the inner part of the image

min_magnitude: minimum magnitude of stars for catalog search

name: name of ImageSolver

process(spotlist, exposure, estimated_pointing=None, fov_radius=None, image_solution=None)

Solve the image given an exposure object.

Parameters:

spotlist (SpotList) – List of pixel coordinates of extracted spots
exposure (Exposure) – Exposure object. Should be removed at some point.
estimated_pointing (SkyCoord[RADec]) – guess of the optical axis pointing of the telescope. If None, try exposure.nominal_telescope_pointing
fov_radius (Angle or None) – radius of the field of view (for star matching) If set to None, estimated FoV from camera parameters
image_solution (ctapointing.imagesolver.ImageSolution) – object that is to be updated by the results of the image solving process. If None, new ImageSolution object is created and returned by this method.

Return type:

Tuple of Registration object and best-match Quad object

scale_tolerance: allowed deviation in true vs. nominal focal length of camera

uuid: UUID of ImageSolver