punchbowl.level1.destreak#

Functions#

streak_correction_matrix(→ numpy.ndarray)

Compute a matrix used in correcting streaks in PUNCH images.

correct_streaks(→ numpy.ndarray)

Corrects an image for streaks.

destreak_task(→ ndcube.NDCube)

Prefect task to destreak an image.

Module Contents#

punchbowl.level1.destreak.streak_correction_matrix(n: int, exposure_time: float, readout_line_time: float, reset_line_time: float) → numpy.ndarray#

Compute a matrix used in correcting streaks in PUNCH images.

Computes the inverse of a matrix of size n where the major diagonal contains the value exposure_time, the lower triangle contains readout_line_time and the upper triangle contains the reset_line_time. i.e. X[i,i]=diag, X[0:i-1,i]=below, X[0,i+1:n-1]=above

Adapted from solarsoft sc_inverse

Parameters:

  • n (int) – size of the matrix (n x n)

  • exposure_time (float) – the exposure time, i.e. value on the diagonal of the matrix

  • readout_line_time (float) – the readout line time, i.e. value in the lower triangle

  • reset_line_time (float) – the reset line time, i.e. value in the upper triangle

Returns:

value of specified streak correction array

Return type:

np.ndarray

Raises:

np.linalg.LinAlgError – Singular matrix: Matrix isn’t invertible

Notes

As long as the units are consistent, this should work. For PUNCH, we use milliseconds.

Examples

>>> streak_correction_matrix(3, 1, 2, 3)
array([[-0.38461538,  0.23076923,  0.46153846],
       [ 0.30769231, -0.38461538,  0.23076923],
       [ 0.15384615,  0.30769231, -0.38461538]])
punchbowl.level1.destreak.correct_streaks(image: numpy.ndarray, exposure_time: float, readout_line_time: float, reset_line_time: float) → numpy.ndarray#

Corrects an image for streaks.

Parameters:

  • image (np.ndarray (2D)) – image to be corrected

  • exposure_time (float) – exposure time in consistent units (e.g. milliseconds) with readout_line_time and reset_line time

  • readout_line_time (float) – time to read out a line in consistent units (e.g. milliseconds) with exposure_time and reset_line time

  • reset_line_time (float) – time to reset CCD in consistent units (e.g. milliseconds) with readout_line_time and exposure_time

Returns:

a streak-corrected image

Return type:

np.ndarray

Raises:

  • ValueError – If the image is not 2D or not square

  • TypeError – If the image is not a numpy array

  • np.linalg.LinAlgError – Singular matrix: Matrix isn’t invertible

Examples

>>> correct_streaks(np.arange(9).reshape(3,3), 1, 2, 3)
array([[ 3.46153846,  3.76923077,  4.07692308],
   [ 0.23076923,  0.38461538,  0.53846154],
   [-1.38461538, -1.30769231, -1.23076923]])
punchbowl.level1.destreak.destreak_task(data_object: ndcube.NDCube, exposure_time: float = 1.0, readout_line_time: float = 0.1, reset_line_time: float = 0.1) → ndcube.NDCube#

Prefect task to destreak an image.