The visir_spc_obs_ech recipe

visir_spc_obs_ech

Synopsis

Spectroscopic observation recipe in Echelle mode

Description

This recipe estimates the dispersion relation using the atmospheric spectrum in a grism spectroscopy half-cycle frame.

It also extracts the spectrum of an observed object using a combined frame.

The files listed in the Set Of Frames (sof-file) must be tagged: VISIR-Echelle-Spectroscopy-file.fits SPEC_OBS_HRG VISIR-Quantum-Efficiency-Calibration-file.fits SPEC_CAL_QEFF VISIR-Atmospheric-Emission-Lines-Calibration-file.fits SPEC_CAL_LINES

Additionally, a bad pixel map with a PRO.CATG of SPEC_BPM may be added to the Set Of Frames with tag: BPM.

Constructor

cpl.Recipe("visir_spc_obs_ech")

Create an object for the recipe visir_spc_obs_ech.

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

Parameters

visir_spc_obs_ech.param.nod

An optional ASCII specification of the nodding positions (in case they are missing from the FITS-file). The file must consist of one line per input FITS-file and each line must consist of an integer (which is ignored) followed by a 0 or 1 (to indicate object or sky). (str; default: ‘’) [default=”“].

visir_spc_obs_ech.param.auto_bpm

Automatic detection and correction of bad pixels (bool; default: True) [default=True].

visir_spc_obs_ech.param.g

Automatic filtering of glitches (bool; default: False) [default=False].

visir_spc_obs_ech.param.p

Automatic purging of half-cycle images whose median deviates more than a factor three from the mean of the medians of half-cycle images or whose standard deviation deviates more than a factor three from the mean of their standard deviations (bool; default: False) [default=False].

visir_spc_obs_ech.param.union

Combine images using their union, as opposed to their intersection (deprecated and ignored, see –combine_method) (bool; default: True) [default=True].

visir_spc_obs_ech.param.rej

Each resulting pixel is the average of the corresponding (interpolated) pixel value in each jittered image. A positive value, n1, for the first of the two integers specifies that for each pixel the smallest n1 pixel values shall be ignored in the averaging. Similarly, a positive value, n2, for the second of the two integers specifies that for each pixel the largest n2 pixel values shall be ignored in the averaging. (str; default: ‘0-0’) [default=”0-0”].

visir_spc_obs_ech.param.plot

The recipe can produce a number of predefined plots. Zero means that none of the plots are produced, while increasing values (e.g. 1 or 2) increases the number of plots produced. If the plotting fails a warning is produced, and the recipe continues. The default behaviour of the plotting is to use gnuplot (with option -persist). The recipe currently produces 1D-plots using gnuplot commands. The recipe user can control the actual plotting-command used by the recipe to create the plot by setting the environment variable CPL_PLOTTER. Currently, if CPL_PLOTTER is set it must contain the string ‘gnuplot’. Setting it to ‘cat > my_gnuplot_$$.txt’ causes a number of ASCII-files to be created, which each produce a plot when given as standard input to gnuplot (e.g. later or on a different computer). A finer control of the plotting options can be obtained by writing an executable script, e.g. my_gnuplot.pl, that executes gnuplot after setting the desired gnuplot options (e.g. set terminal pslatex color) and then setting CPL_PLOTTER to my_gnuplot.pl. The predefined plots include plotting of images. Images can be plotted not only with gnuplot, but also using the pnm format. This is controlled with the environment variable CPL_IMAGER. If CPL_IMAGER is set to a string that does not contain the word gnuplot, the recipe will generate the plot in pnm format. E.g. setting CPL_IMAGER to ‘display - &’ will produce a gray-scale image using the image viewer display. (long; default: 0) [default=0].

visir_spc_obs_ech.param.slit_skew

Distortion correction: Skew of slit (degrees) (clockwise) (float; default: 0.0) [default=0.0].

visir_spc_obs_ech.param.spectrum_skew

Distortion correction: LMR Skew of spectrum (degrees) (counter- clockwise). Not used in High Resolution (float; default: 0.0) [default=0.0].

visir_spc_obs_ech.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: 0.0) [default=0.0].

visir_spc_obs_ech.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].

visir_spc_obs_ech.param.orderoffset

Echelle order offset. The offset is relative to the main order. The allowed range of offsets depend on the selected grism. The offset can never exceed +/-4. If the main order is e.g. 8 an order offset of +1 will cause the recipe to base the data reduction on order 9. With a positive order offset the central wavelength becomes smaller while for a negative order offset the central wavelength becomes larger. (long; default: 0) [default=0].

visir_spc_obs_ech.param.off

An optional ASCII specification of the offsets in case those in FITS- headers are missing or wrong. The file must consist of one line per input pair of FITS-files, and each line must consist of two numbers which represent the shift in pixels of that image relative to the first image. The first line should thus comprise two zeros. Correct FITS-header offsets mean that the i’th X offset can be gotten from Xoffset_0 - Xoffset_i, where Xoffset_i is the value of ESO SEQ CUMOFFSETX and likewise for Y. (str; default: ‘’) [default=”“].

visir_spc_obs_ech.param.ref

User-defined refining of the image offsets. See options objs and xcorr (bool; default: False) [default=False].

visir_spc_obs_ech.param.objs

The shift and add of images needs anchor points that typically are bright objects. These are normally detected automatically but with user-defined refining of offsets enabled, they must be provided by the user through an ASCII file containing one line per anchor point with each line consisting of its x and y coordinate (in pixels). This file is ignored with user-defined refining of offsets disabled. (str; default: ‘’) [default=”“].

visir_spc_obs_ech.param.xcorr

If user-defined refining of offsets is enabled a cross-correlation of the images is performed. In order to speed up this process, this cross-correlation is performed only on smaller rectangles around the anchor points. The first two parameters is the half-size of this rectangle in pixels. The second pair is the maximum shift in x and y (pixels) evaluated by the cross-correlation on the rectangle. Used only if user-defined refining of offsets is enabled. (str; default: ‘10-10-25-25’) [default=”10-10-25-25”].

visir_spc_obs_ech.param.fixcombi

Perform the distortion correction on the combined image, and not on each of the jittered images. This will reduce excution time and degrade the quality of the combined image (bool; default: False) [default=False].

visir_spc_obs_ech.param.destripe_iterations

Max number of destriping iterations (0 to disable destriping). Horizontal destriping is done first and if no horizontal striping is detected, vertical destriping is performed (long; default: 15) [default=15].

visir_spc_obs_ech.param.destripe_morpho

Destripe with morphological cleaning (bool; default: False) [default=False].

visir_spc_obs_ech.param.rl

Reject leftmost columns in spectrum extraction, zero means all columns on the left are used. In cross-dispersion mode a (small) negative number may be used (pixel) (long; default: 0) [default=0].

visir_spc_obs_ech.param.rr

Reject rightmost columns in spectrum extraction, zero means all columns on the right are used. In cross-dispersion mode a (small) negative number may be used (pixel) (long; default: 0) [default=0].

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

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

visir_spc_obs_ech.param.nod = ""
visir_spc_obs_ech.param.auto_bpm = True
visir_spc_obs_ech.param.g = False
visir_spc_obs_ech.param.p = False
visir_spc_obs_ech.param.union = True
visir_spc_obs_ech.param.rej = "0-0"
visir_spc_obs_ech.param.plot = 0
visir_spc_obs_ech.param.slit_skew = 0.0
visir_spc_obs_ech.param.spectrum_skew = 0.0
visir_spc_obs_ech.param.vert_arc = 0.0
visir_spc_obs_ech.param.hori_arc = 0.0
visir_spc_obs_ech.param.orderoffset = 0
visir_spc_obs_ech.param.off = ""
visir_spc_obs_ech.param.ref = False
visir_spc_obs_ech.param.objs = ""
visir_spc_obs_ech.param.xcorr = "10-10-25-25"
visir_spc_obs_ech.param.fixcombi = False
visir_spc_obs_ech.param.destripe_iterations = 15
visir_spc_obs_ech.param.destripe_morpho = False
visir_spc_obs_ech.param.rl = 0
visir_spc_obs_ech.param.rr = 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_spc_obs_ech = cpl.Recipe("visir_spc_obs_ech")
[...]
res = visir_spc_obs_ech( ..., param = {"nod":"", "auto_bpm":True})

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.