PointingCamera

class ctapointing.camera.PointingCamera(**kwargs: Any)

Bases: Component

Pointing camera class.

Hosts routines and parameters necessary to project Alt-Az coordinates into the chip plane.

Uses correct tangential projection into the chip plane (i.e. no small-angle approximation). Takes account for the orientation of the telescope (in Alt-Az coordinates), rotation of the camera w.r.t. the horizon, a tilt of the camera’s optical axis w.r.t. the telescope pointing, and possible shifts of the chip centre w.r.t. the optical axis and lens distortions.

The camera coordinate system has its origin exactly at the centre of the chip (for chips with odd number of pixels in the middle of the central pixel, for chips with even number of pixels at the boundary between the two innermost pixels).

Transformation of camera coordinates into chip coordinates follows the FITS/astropy standard, in which integer pixel coordinates are at the centre of a pixel, with pixel index 0 covering the range [-0.5, 0.5], representing physical pixel 1.

x points from bottom to top of the up-right chip, when viewing from the chip into the scene; y points from left to right.

By default, a ctapointing.camera.DistortionCorrectionNull model is loaded as the default for the correction of lens distortions. Any other DistortionCorrection model can be applied by adding it as a sub-component of the camera config in the configuration file.

Parameters:

uuid (Unicode) – UUID of the camera
name (Unicode) – name of the camera
location (astropy.coordinates.EarthLocation) – location of the camera on Earth
f_stop (Float) – f_stop of the lens (focal length / aperture diameter)
num_pix (List of Int: number of pixels in x and y)
pixel_size (AstroQuantity[length]) – size of a pixel edge
tilt (AstroQuantity[angle]) – camera tilt w.r.t. telescope orientation (x/y)
offset (AstroQuantity[length]) – offset of chip centre w.r.t. telescope orientation (x/y)
rotation (AstroQuantity[angle]) – rotation of the camera around optical axis
noise_mean (List[float]) – list of mean noise values (one per pixel fraction)
noise_rms (List[float]) – list of rms noise values (one per pixel fraction)
noise_pixel_fraction (List[Float]) – list of pixel fractions
expansion_coefficient (Float) – chip expansion coefficient
efficiency (Float) – pixel efficiency
manufacturer (Unicode) – camera manufacturer
model (Unicode) – camera model
serial_number (Unicode) – camera serial number
telescope_id (Int) – telescope ID
dtype (Enum) – pixel depth (in bits)
used_since (AstroTime) – date and time of first operation
used_until (AstroTime) – date and time of decommissioning

Attributes Summary

`aperture`	Aperture of the camera lens.
`bit_depth`	pixel depth (bits)
`chip_area`	Camera chip area (in physical units).
`chip_centre`	Camera chip centre in physical pixel coordinates.
`chip_size`	Camera chip size (in physical units).
`efficiency`	pixel efficiency
`expansion_coefficient`	chip expansion coefficient
`f_stop`	f-stop of lens
`focal_length`	focal length of lens (x/y chip direction)
`fov`	Angular field of view.
`fov_plane_projected`	Field of view, projected onto a tangent plane of the unit sphere.
`location`	earth location of camera, either 'x, y, z' in geocentriccoordinates or site location string
`manufacturer`	camera manufacturer
`model`	camera model
`name`	camera name
`noise_mean`	list of mean noise values (one per pixel fraction)
`noise_pixel_fraction`	list of pixel fractions
`noise_rms`	list of rms noise values (one per pixel fraction)
`num_pix`	camera chip number of pixels (x/y chip direction
`offset`	offset of chip centre w.r.t.
`pixel_angle`	Angle covered by a pixel edge in units of arcsec
`pixel_size`	camera pixel size
`pixel_solid_angle`	Returns the solid angle of a pixel in units of arc seconds squared
`rotation`	rotation of camera w.r.t.
`serial_number`	camera serial number
`telescope_id`	telescope ID
`tilt`	camera tilt w.r.t.
`used_since`	date of first usage
`used_until`	date of decommissioning
`uuid`	UUID of Camera

Methods Summary

`clip_to_chip`(pix_coords[, tolerance])	Clip an array of pixel coordinates to those coordinates which are inside the chip boundaries.
`from_config`(**kwargs)	Read a camera configuration from either configuration file or database.
`project_from`(coords, obstime, telescope_pointing)	Project given SkyCameraFrame coordinates back to AltAz.
`project_into`(coords, telescope_pointing[, ...])	Project a given array of altaz coordinates into the pointing camera chip.
`transform_to_camera`(coords_pix)	Transform coordinates from the pixel system to the SkyCameraFrame.
`transform_to_pixels`(coords_cam)	Transform coordinates from the SkyCameraFrame to pixel coordinates.

Attributes Documentation

aperture

Aperture of the camera lens.

Returns:: aperture – lens aperture in millimeter-squared
Return type:: astropy.Quantity

bit_depth: pixel depth (bits)

chip_area

Camera chip area (in physical units).

Returns:: area – chip area
Return type:: astropy.Quantity

chip_centre

Camera chip centre in physical pixel coordinates.

for odd number of pixels, the chip centre is located at the centre of the central pixel, hence the centre corresponds to an integer in physical pixel coordinates
for even number of pixels, the chip centre is in between the innermost pixels, hence the centre corresponds to an integer+0.5 in physical pixel coordinates
the pixel with index 0 covers the coordinate range [-0.5, 0.5]

Returns:: (centre_x, centre_y) – physical pixel coordinates of chip centre
Return type:: array of floats

chip_size

Camera chip size (in physical units).

Returns:: (size_x, size_y) – size along x and y axes
Return type:: tuple of astropy.Quantity

efficiency: pixel efficiency

expansion_coefficient: chip expansion coefficient

f_stop: f-stop of lens

focal_length: focal length of lens (x/y chip direction)

fov

Angular field of view.

Returns:: (fov_x, fov_y) – field of view along x and y direction
Return type:: tuple of astropy.Angle

fov_plane_projected

Field of view, projected onto a tangent plane of the unit sphere.

Returns:: (fov_x, fov_y) – field of view along x and y direction, plane projected
Return type:: tuple of astropy.Angle

location: earth location of camera, either ‘x, y, z’ in geocentriccoordinates or site location string

manufacturer: camera manufacturer

model: camera model

name: camera name

noise_mean: list of mean noise values (one per pixel fraction)

noise_pixel_fraction: list of pixel fractions

noise_rms: list of rms noise values (one per pixel fraction)

num_pix: camera chip number of pixels (x/y chip direction

offset: offset of chip centre w.r.t. telescope orientation (x/y)

pixel_angle

Angle covered by a pixel edge in units of arcsec

Returns:: angle – angle in arc seconds
Return type:: astropy.Quantity

pixel_size: camera pixel size

pixel_solid_angle

Returns the solid angle of a pixel in units of arc seconds squared

Returns:: solid_angle – solid angle in arc seconds squared
Return type:: astropy.Quantity

rotation: rotation of camera w.r.t. horizon, in degrees

serial_number: camera serial number

telescope_id: telescope ID

tilt: camera tilt w.r.t. telescope orientation (x/y)

used_since: date of first usage

used_until: date of decommissioning

uuid: UUID of Camera

Methods Documentation

clip_to_chip(pix_coords, tolerance=0)

Clip an array of pixel coordinates to those coordinates which are inside the chip boundaries.

Parameters:

pix_coords (array) – 2D array of pixel coordinates
tolerance (float) – tolerance in units of pixels

Returns:

mask – boolean array of same shape as pix_coords, with positions which are inside the chip boundaries (and within tolerance) set to True (and False otherwise)

Return type:

numpy.array

classmethod from_config(**kwargs)

Read a camera 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 camera (as in PointingCamera.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 PointingCamera.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:

camera

Return type:

PointingCamera object

project_from(coords, obstime, telescope_pointing)

Project given SkyCameraFrame coordinates back to AltAz.

Parameters:

coords (SkyCoord in SkyCameraFrame) – coordinates on CCD chip in SkyCameraFrame
obstime (Astropy.Time) – time of the observation
telescope_pointing (SkyCoord) – telescope pointing direction

Returns:

coords_altaz – transformed coordinates in the AltAz system

Return type:

SkyCoord

project_into(coords, telescope_pointing, use_obstime_of_first_coordinate=True)

Project a given array of altaz coordinates into the pointing camera chip. Takes current camera orientation, camera intrinsic parameters and distortions into account.

Parameters:

coords (array(astropy.SkyCoord)) – array of sky coordinates in the AltAz system
telescope_pointing (astropy.SkyCoord) – telescope pointing position (RADec or AltAz system)
use_obstime_of_first_coordinate (bool) – use observation time of the first coordinate if array of SkyCoords is provided. This reduces computation time by a lot, and should be the default for coordinates that are part of the same image.

Returns:

coords_proj (SkyCoord) – 2D projections in chip coordinates (in SkyCameraFrame)
todo (star projection is wrong when translation t is switched on. This happens because)
the altaz position of the (infinitely) distant star is converted to a vector on the
unit circle. Should explicitly distinguish between star projection and projection of
world objects.

transform_to_camera(coords_pix)

Transform coordinates from the pixel system to the SkyCameraFrame.

Parameters:: coords_pix (2D array of pixel coordinates)
Returns:: cam_coords – coordinates in SkyCameraFrame
Return type:: SkyCoord

transform_to_pixels(coords_cam)

Transform coordinates from the SkyCameraFrame to pixel coordinates.

Parameters:: coords_cam (SkyCoord) – coordinates in the SkyCameraFrame
Returns:: coords_pix – 2D array of pixel coordinates
Return type:: numpy.array

__init__(config=None, parent=None, **kwargs)

Parameters:

config (traitlets.loader.Config) – Configuration specified by config file or cmdline arguments. Used to set traitlet values.
parent (Tool or Component) – If a Component is created by another Component or Tool, you need to pass the creating Component as parent, e.g. parent=self. This makes sure the config is correctly handed down to the child components. Do not pass config in this case.
kwargs – Traitlets to be overridden. TraitError is raised if kwargs contains a key that does not correspond to a traitlet.

property aperture

Aperture of the camera lens.

Returns:: aperture – lens aperture in millimeter-squared
Return type:: astropy.Quantity

bit_depth: pixel depth (bits)

property chip_area

Camera chip area (in physical units).

Returns:: area – chip area
Return type:: astropy.Quantity

property chip_centre

Camera chip centre in physical pixel coordinates.

for odd number of pixels, the chip centre is located at the centre of the central pixel, hence the centre corresponds to an integer in physical pixel coordinates
for even number of pixels, the chip centre is in between the innermost pixels, hence the centre corresponds to an integer+0.5 in physical pixel coordinates
the pixel with index 0 covers the coordinate range [-0.5, 0.5]

Returns:: (centre_x, centre_y) – physical pixel coordinates of chip centre
Return type:: array of floats

property chip_size

Camera chip size (in physical units).

Returns:: (size_x, size_y) – size along x and y axes
Return type:: tuple of astropy.Quantity

clip_to_chip(pix_coords, tolerance=0)

Clip an array of pixel coordinates to those coordinates which are inside the chip boundaries.

Parameters:

pix_coords (array) – 2D array of pixel coordinates
tolerance (float) – tolerance in units of pixels

Returns:

mask – boolean array of same shape as pix_coords, with positions which are inside the chip boundaries (and within tolerance) set to True (and False otherwise)

Return type:

numpy.array

efficiency: pixel efficiency

expansion_coefficient: chip expansion coefficient

f_stop: f-stop of lens

focal_length: focal length of lens (x/y chip direction)

property fov

Angular field of view.

Returns:: (fov_x, fov_y) – field of view along x and y direction
Return type:: tuple of astropy.Angle

property fov_plane_projected

Field of view, projected onto a tangent plane of the unit sphere.

Returns:: (fov_x, fov_y) – field of view along x and y direction, plane projected
Return type:: tuple of astropy.Angle

classmethod from_config(**kwargs)

Read a camera 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 camera (as in PointingCamera.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 PointingCamera.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:

camera

Return type:

PointingCamera object

location: earth location of camera, either ‘x, y, z’ in geocentriccoordinates or site location string

manufacturer: camera manufacturer

model: camera model

name: camera name

noise_mean: list of mean noise values (one per pixel fraction)

noise_pixel_fraction: list of pixel fractions

noise_rms: list of rms noise values (one per pixel fraction)

num_pix: camera chip number of pixels (x/y chip direction

offset: offset of chip centre w.r.t. telescope orientation (x/y)

property pixel_angle

Angle covered by a pixel edge in units of arcsec

Returns:: angle – angle in arc seconds
Return type:: astropy.Quantity

pixel_size: camera pixel size

property pixel_solid_angle

Returns the solid angle of a pixel in units of arc seconds squared

Returns:: solid_angle – solid angle in arc seconds squared
Return type:: astropy.Quantity

project_from(coords, obstime, telescope_pointing)

Project given SkyCameraFrame coordinates back to AltAz.

Parameters:

coords (SkyCoord in SkyCameraFrame) – coordinates on CCD chip in SkyCameraFrame
obstime (Astropy.Time) – time of the observation
telescope_pointing (SkyCoord) – telescope pointing direction

Returns:

coords_altaz – transformed coordinates in the AltAz system

Return type:

SkyCoord

project_into(coords, telescope_pointing, use_obstime_of_first_coordinate=True)

Project a given array of altaz coordinates into the pointing camera chip. Takes current camera orientation, camera intrinsic parameters and distortions into account.

Parameters:

coords (array(astropy.SkyCoord)) – array of sky coordinates in the AltAz system
telescope_pointing (astropy.SkyCoord) – telescope pointing position (RADec or AltAz system)
use_obstime_of_first_coordinate (bool) – use observation time of the first coordinate if array of SkyCoords is provided. This reduces computation time by a lot, and should be the default for coordinates that are part of the same image.

Returns:

coords_proj (SkyCoord) – 2D projections in chip coordinates (in SkyCameraFrame)
todo (star projection is wrong when translation t is switched on. This happens because)
the altaz position of the (infinitely) distant star is converted to a vector on the
unit circle. Should explicitly distinguish between star projection and projection of
world objects.

rotation: rotation of camera w.r.t. horizon, in degrees

serial_number: camera serial number

telescope_id: telescope ID

tilt: camera tilt w.r.t. telescope orientation (x/y)

transform_to_camera(coords_pix)

Transform coordinates from the pixel system to the SkyCameraFrame.

Parameters:: coords_pix (2D array of pixel coordinates)
Returns:: cam_coords – coordinates in SkyCameraFrame
Return type:: SkyCoord

transform_to_pixels(coords_cam)

Transform coordinates from the SkyCameraFrame to pixel coordinates.

Parameters:: coords_cam (SkyCoord) – coordinates in the SkyCameraFrame
Returns:: coords_pix – 2D array of pixel coordinates
Return type:: numpy.array

used_since: date of first usage

used_until: date of decommissioning

uuid: UUID of Camera