The visir_util_undistort recipe

visir_util_undistort

Synopsis

Correct the distortion in spectral data

Description

The files listed in the Set Of Frames (sof-file) must be tagged: VISIR-chopnod-corrected-file.fits CHOPNOD_CORRECTED Optionally, a bad pixel map may be provided: VISIR-bpm-file.fits STATIC_MASK

The product(s) will have a FITS card ‘HIERARCH ESO PRO CATG’ with a value of: UNDISTORTED The recipe default values for the transformation are only valid for spectral data taken in Low resolution mode

Constructor

cpl.Recipe("visir_util_undistort")

Create an object for the recipe visir_util_undistort.

import cpl
visir_util_undistort = cpl.Recipe("visir_util_undistort")

Parameters

visir_util_undistort.param.bkgcorrect

Cho-nod correct the data (bool; default: True) [default=True].

visir_util_undistort.param.xl

Coordinate in spatial direction. Together with yl it defines the lower point of a rectangle containing only skylines for the wavelength shift detection (int; default: 117) [default=117].

visir_util_undistort.param.yl

Coordinate in wavelength direction. See xl (int; default: 110) [default=110].

visir_util_undistort.param.xh

Coordinate in spatial direction. Together with yl it defines the higher point of a rectangle containing only skylines for the wavelength shift detection (int; default: 125) [default=125].

visir_util_undistort.param.yh

Coordinate in wavelength direction. See xh (int; default: 150) [default=150].

visir_util_undistort.param.slit_skew

Distortion correction: Skew of slit (degrees) (clockwise) (float; default: 0.52) [default=0.52].

visir_util_undistort.param.spectrum_skew

Distortion correction: LMR Skew of spectrum (degrees) (counter- clockwise). Not used in High Resolution (float; default: 1.73) [default=1.73].

visir_util_undistort.param.vert_arc

Distortion correction: LR Detector vertical curvature (pixel). Reduced by a factor 4 in MR. Not used in HR A-side. Increased by a factor 115/52 in HR B-side (float; default: -0.8) [default=-0.8].

visir_util_undistort.param.hori_arc

Distortion correction: LMR Detector horizontal curvature (pixel). Increased by a factor 1.5 in HR A-side. Reduced by a factor 2 in HR B-side (float; default: 0.0) [default=0.0].

The following code snippet shows the default settings for the available parameters.

import cpl
visir_util_undistort = cpl.Recipe("visir_util_undistort")

visir_util_undistort.param.bkgcorrect = True
visir_util_undistort.param.xl = 117
visir_util_undistort.param.yl = 110
visir_util_undistort.param.xh = 125
visir_util_undistort.param.yh = 150
visir_util_undistort.param.slit_skew = 0.52
visir_util_undistort.param.spectrum_skew = 1.73
visir_util_undistort.param.vert_arc = -0.8
visir_util_undistort.param.hori_arc = 0.0

You may also set or overwrite some or all parameters by the recipe parameter param, as shown in the following example:

import cpl
visir_util_undistort = cpl.Recipe("visir_util_undistort")
[...]
res = visir_util_undistort( ..., param = {"bkgcorrect":True, "xl":117})

See also

cpl.Recipe for more information about the recipe object.

Bug reports

Please report any problems to Lars Lundin. Alternatively, you may send a report to the ESO User Support Department.