opticam.background.local_background

Classes

BaseLocalBackground

Base class for local background estimators.

DefaultLocalBackground

Default local background estimator using an elliptical annulus.

Module Contents

class opticam.background.local_background.BaseLocalBackground(r_in_scale=5, r_out_scale=7.5, sigma_clip=SigmaClip(sigma=3, maxiters=10))

Bases: abc.ABC

Base class for local background estimators.

Parameters:

  • r_in_scale (float)

  • r_out_scale (float)

  • sigma_clip (None | astropy.stats.SigmaClip)

r_in_scale = 5
r_out_scale = 7.5
sigma_clip
abstractmethod __call__(data, position, semimajor_axis, semiminor_axis, theta)

Compute the local background and its error at a given position (per pixel).

Parameters

dataNDArray

The image data.

semimajor_axisfloat

The (unscaled) semi-major axis of the aperture.

semiminor_axisfloat

The (unscaled) semi-minor axis of the aperture.

thetafloat

The rotation angle of the PSF.

positionTuple[float, float]

The x, y position at which to compute the local background.

Returns

Tuple[float, float]

The local background and its error per pixel.

Parameters:

  • data (numpy.typing.NDArray)

  • position (numpy.typing.NDArray)

  • semimajor_axis (float)

  • semiminor_axis (float)

  • theta (float)

Return type:

Tuple[float, float]

abstractmethod get_annulus(position, semimajor_axis, semiminor_axis, theta)

Define an annulus at the given position.

Parameters

positionNDArray

The centre of the annulus.

semimajor_axisfloat

The semimajor standard deviation of the PSF.

semiminor_axisfloat

The semiminor standard deviation of the PSF.

thetafloat

The orientation of the source in radians.

Returns

Aperture

The annulus.

Parameters:

  • position (numpy.typing.NDArray)

  • semimajor_axis (float)

  • semiminor_axis (float)

  • theta (float)

Return type:

photutils.aperture.Aperture

get_stats(data, position, semimajor_axis, semiminor_axis, theta)

Get the stats of the annulus.

Parameters

dataNDArray

The image data.

positionNDArray

The centre of the annulus.

semimajor_axisfloat

The semimajor standard deviation of the PSF.

semiminor_axisfloat

The semiminor standard deviation of the PSF.

thetafloat

The orientation of the source in radians.

Returns

ApertureStats

The stats of the annulus.

Parameters:

  • data (numpy.typing.NDArray)

  • position (numpy.typing.NDArray)

  • semimajor_axis (float)

  • semiminor_axis (float)

  • theta (float)

Return type:

photutils.aperture.ApertureStats

class opticam.background.local_background.DefaultLocalBackground(r_in_scale=5, r_out_scale=7.5, sigma_clip=SigmaClip(sigma=3, maxiters=10))

Bases: BaseLocalBackground

Default local background estimator using an elliptical annulus.

Parameters:

  • r_in_scale (float)

  • r_out_scale (float)

  • sigma_clip (None | astropy.stats.SigmaClip)

get_annulus(position, semimajor_axis, semiminor_axis, theta)

Define an annulus at the given position.

Parameters

positionNDArray

The centre of the annulus.

semimajor_axisfloat

The semimajor standard deviation of the PSF.

semiminor_axisfloat

The semiminor standard deviation of the PSF.

thetafloat

The orientation of the source in radians.

Returns

Aperture

The annulus.

Parameters:

  • position (numpy.typing.NDArray)

  • semimajor_axis (float)

  • semiminor_axis (float)

  • theta (float)

Return type:

photutils.aperture.Aperture

__call__(data, position, semimajor_axis, semiminor_axis=None, theta=0.0)

Compute the sigma-clipped local background (mean) and its error (standard deviation) at a given position.

Parameters

dataNDArray

The image data.

errorNDArray

The error in the image data.

positionNDArray

The x, y position at which to compute the local background.

semimajor_axisfloat

The (unscaled) semimajor axis of the aperture.

semiminor_axisfloat | None, optional

The (unscaled) semiminor axis of the aperture, by default None. If None, it is assumed to be equal to the semimajor axis (i.e., the annulus is circular).

thetafloat, optional

The rotation angle of the PSF, by default 0 (i.e., no rotation).

Returns

Tuple[float, float]

The local background (mean) and its error (standard deviation).

Parameters:

  • data (numpy.typing.NDArray)

  • position (numpy.typing.NDArray)

  • semimajor_axis (float)

  • semiminor_axis (float | None)

  • theta (float)

Return type:

Tuple[float, float]