Background¶

class specreduce.background.Background(image: ~astropy.nddata.nddata.NDData, traces: list = <factory>, width: float = 5, statistic: str = 'average', disp_axis: int = 1, crossdisp_axis: int = 0)[source]¶

Bases: _ImageParser

Determine the background from an image for subtraction.

Example:

trace = FlatTrace(image, trace_pos)
bg = Background.two_sided(image, trace, bkg_sep, width=bkg_width)
subtracted_image = image - bg

Parameters:

imageNDData-like or array-like: image with 2-D spectral image data
tracestrace, int, float (single or list): Individual or list of trace object(s) (or integers/floats to define FlatTraces) to extract the background. If None, a FlatTrace at the center of the image (according to disp_axis) will be used.
widthfloat: width of extraction aperture in pixels
statistic: string: statistic to use when computing the background. ‘average’ will account for partial pixel weights, ‘median’ will include all partial pixels.
disp_axisint: dispersion axis
crossdisp_axisint: cross-dispersion axis

Attributes Summary

`bkg_array`	Deprecated since version 1.3.
`crossdisp_axis`
`disp_axis`
`statistic`
`width`

Methods Summary

`bkg_image`([image])	Expose the background tiled to the dimension of `image`.
`bkg_spectrum`([image])	Expose the 1D spectrum of the background.
`one_sided`(image, trace_object, separation, ...)	Determine the background from an image for subtraction above or below an input trace.
`sub_image`([image])	Subtract the computed background from `image`.
`sub_spectrum`([image])	Expose the 1D spectrum of the background-subtracted image.
`two_sided`(image, trace_object, separation, ...)	Determine the background from an image for subtraction centered around an input trace.

Attributes Documentation

bkg_array¶: Deprecated since version 1.3: The bkg_array attribute is deprecated and may be removed in a future version.

crossdisp_axis: int = 0¶

disp_axis: int = 1¶

statistic: str = 'average'¶

width: float = 5¶

Methods Documentation

bkg_image(image=None)[source]¶

Expose the background tiled to the dimension of image.

Parameters:

imageNDData-like or array-like, optional: Image with 2-D spectral image data. Assumes cross-dispersion (spatial) direction is axis 0 and dispersion (wavelength) direction is axis 1. If None, will extract the background from image used to initialize the class. [default: None]

Returns:

Spectrum1D object with same shape as image.

bkg_spectrum(image=None)[source]¶

Expose the 1D spectrum of the background.

Parameters:

imageNDData-like or array-like, optional: Image with 2-D spectral image data. Assumes cross-dispersion (spatial) direction is axis 0 and dispersion (wavelength) direction is axis 1. If None, will extract the background from image used to initialize the class. [default: None]

Returns:

specSpectrum1D: The background 1-D spectrum, with flux expressed in the same units as the input image (or u.DN if none were provided) and the spectral axis expressed in pixel units.

classmethod one_sided(image, trace_object, separation, **kwargs)[source]¶

Determine the background from an image for subtraction above or below an input trace.

Example:

trace = FitTrace(image, guess=trace_pos)
bg = Background.one_sided(image, trace, bkg_sep, width=bkg_width)

Parameters:

imageNDData-like or array-like: Image with 2-D spectral image data. Assumes cross-dispersion (spatial) direction is axis 0 and dispersion (wavelength) direction is axis 1.
trace_object: `~specreduce.tracing.Trace`: estimated trace of the spectrum to center the background traces
separation: float: separation from trace_object for the background, positive will be above the trace, negative below.
widthfloat: width of each background aperture in pixels
statistic: string: statistic to use when computing the background. ‘average’ will account for partial pixel weights, ‘median’ will include all partial pixels.
disp_axisint: dispersion axis
crossdisp_axisint: cross-dispersion axis

sub_image(image=None)[source]¶

Subtract the computed background from image.

Parameters:

imagenddata-compatible image or None: image with 2-D spectral image data. If None, will extract the background from image used to initialize the class.

Returns:

Spectrum1D object with same shape as image.

sub_spectrum(image=None)[source]¶

Expose the 1D spectrum of the background-subtracted image.

Parameters:

imagenddata-compatible image or None: image with 2-D spectral image data. If None, will extract the background from image used to initialize the class.

Returns:

specSpectrum1D: The background 1-D spectrum, with flux expressed in the same units as the input image (or u.DN if none were provided) and the spectral axis expressed in pixel units.

classmethod two_sided(image, trace_object, separation, **kwargs)[source]¶

Determine the background from an image for subtraction centered around an input trace.

Example:

trace = FitTrace(image, guess=trace_pos)
bg = Background.two_sided(image, trace, bkg_sep, width=bkg_width)

Parameters:

imageNDData-like or array-like: Image with 2-D spectral image data. Assumes cross-dispersion (spatial) direction is axis 0 and dispersion (wavelength) direction is axis 1.
trace_object: `~specreduce.tracing.Trace`: estimated trace of the spectrum to center the background traces
separation: float: separation from trace_object for the background regions
widthfloat: width of each background aperture in pixels
statistic: string: statistic to use when computing the background. ‘average’ will account for partial pixel weights, ‘median’ will include all partial pixels.
disp_axisint: dispersion axis
crossdisp_axisint: cross-dispersion axis

Navigation

Background¶