The visir_img_reduce recipe

visir_img_reduce

Synopsis

Combines a stack of chopped, jittered and/or nodded exposures and can compute the sensitivity for standard star observations

Description

This recipe recombines the data observed in chopping/nodding or chopping or nodding modes into one combined image using optionally cross-correlation methods.

The files listed in the Set Of Frames (sof-file) must be tagged: VISIR-observation-file.fits IM_OBS_CHO_NOD_JIT or VISIR-observation-file.fits IM_OBS_CHO_JIT or VISIR-observation-file.fits IM_OBS_NOD_JIT or VISIR-observation-file.fits IM_OBS_DIR_JIT or VISIR-observation-file.fits BURST VISIR-Standard-star-catalog IMG_STD_CATALOG (optional) VISIR-linearty-table.fits LINEARITY_TABLE (optional) Additionally, a bad pixel map with a PRO.CATG of IMG_BPM may be added to the Set Of Frames with tag: BPM.

Constructor

cpl.Recipe("visir_img_reduce")

Create an object for the recipe visir_img_reduce.

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

Parameters

visir_img_reduce.param.planestart

Plane number to start repacking from in each nod cycle,earlier planes are skipped. (int; default: 0) [default=0].

visir_img_reduce.param.planelimit

Limit number of processed inputplanes. It will repack until at least this number of input images have been processed or the full dataset has been repacked. Always full chop cycles need to be repacked so the number is adjusted upward to the next multiple of images per chop cycle. <= 0 for no limit. (int; default: -1) [default=-1].

visir_img_reduce.param.trimlow

Burst data only. Number of additional planes to cut from before each plane with chopper movement. (int; default: 0) [default=0].

visir_img_reduce.param.trimhigh

Burst data only. Number of additional planes to cut from after each plane with chopper movement. A value of -1 does not skip the plane of the movement. (int; default: 0) [default=0].

visir_img_reduce.param.lincorrect

Apply linearity correction. Should only be enabled on high flux observations, may degrade results otherwise. (bool; default: False) [default=False].

visir_img_reduce.param.template

Correlation template used to detect shifts and reject bad images. If none given an averaged image is used (str; default: ‘NONE’) [default=”NONE”].

visir_img_reduce.param.min_correlation

Minimal correlation to the template required to be accepted (float; default: 0.5) [default=0.5].

visir_img_reduce.param.max_shift

Maximal allowed object shift for an image to be accepted (float; default: 10.0) [default=10.0].

visir_img_reduce.param.max_mad

Maximal allowed median absolute deviation for an image to be accepted. <= 0 equals no limit (float; default: 0.0) [default=0.0].

visir_img_reduce.param.naverage

Number of planes to average before attempting to detect the shifts. (int; default: 1) [default=1].

visir_img_reduce.param.method

Method to determine beam shifts. xcorrelate: use the cross correlation shift. brightest: use the position of the brightest pixel (str; default: ‘xcorrelate’) [default=”xcorrelate”].

visir_img_reduce.param.no_shift

Sets whether to apply the determined shifts in following recipes. Set to TRUE of shifts appear too large. (bool; default: False) [default=False].

visir_img_reduce.param.no_reject

If true images with bad statistics will not be rejected and no shift correction is done (bool; default: True) [default=True].

visir_img_reduce.param.beampos

Define the positions of the beams. These positions are cut by the window to extract the single beam images. Format: sign:x,y,window;sign:x,y,window;… where sign is “pos” or “neg” depending on whether the beam is positive or negative. The window is optional and defines the size of the cut image around the beam. The default window is the chop throw. E.g.: pos:50,60;neg:50,160; By default autodetection is attempted. (str; default: ‘NONE’) [default=”NONE”].

visir_img_reduce.param.eccmax

The maximum eccentricity allowed in the combination of the three (in parallel nod/chopping) or four (in perpendicular nod/chopping) beams. In parallel mode, three perfectly aligned points spaced with the chopnod throw will have eccentricity 0, while in perpedicular mode a square with the chopnod throw as the side length will have eccentricity 0 (float; default: 3.0) [default=3.0].

visir_img_reduce.param.keepfrac

The fraction of pixels to keep for the initialmedian (float; default: 0.9) [default=0.9].

visir_img_reduce.param.kappa

Clip outside + or - kappa * sigma (the standard deviation) (float; default: 5.0) [default=5.0].

visir_img_reduce.param.maxite

Max number of kappa-sigma clipping iterations (int; default: 3) [default=3].

visir_img_reduce.param.shift_beams

Account for movements of the object defined in CRPIX[12] (bool; default: True) [default=True].

visir_img_reduce.param.error_source

Defines the way errors are generated: img-stdev: stdev of image timeseries: stdev of each pixel over the time axis of the cube none: no error generation (str; default: ‘img-stdev’) [default=”img-stdev”].

visir_img_reduce.param.badimage

If percentage of clipped pixels above this value the whole image is considered bad (float; default: 0.2) [default=0.2].

visir_img_reduce.param.output_all

Output a coadded image for each input file in addition to the complete coaddition. (bool; default: False) [default=False].

visir_img_reduce.param.extra_config

Additional configuration parameters (str; default: ‘NONE’) [default=”NONE”].

visir_img_reduce.param.config_fname

Swarp configure file name. (str; default: ‘/usr/share/cpl- plugins/visir-4.4.2/config/visir_default.swarp’) [default=”/usr/share/cpl-plugins/visir-4.4.2/config/visir_default.swarp”].

visir_img_reduce.param.nprocs

Maximum number of swarp processes that can be spawned simultaneously. (int; default: -1) [default=-1].

visir_img_reduce.param.jy_val

The flux of the standard star in Jansky (float; default: -999.0) [default=-999.0].

visir_img_reduce.param.radii

Radii : star_max bg_int bg_ext (str; default: ‘20-20-30’) [default=”20-20-30”].

visir_img_reduce.param.delete_temp

Delete temporary files created during processing (bool; default: True) [default=True].

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

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

visir_img_reduce.param.planestart = 0
visir_img_reduce.param.planelimit = -1
visir_img_reduce.param.trimlow = 0
visir_img_reduce.param.trimhigh = 0
visir_img_reduce.param.lincorrect = False
visir_img_reduce.param.template = "NONE"
visir_img_reduce.param.min_correlation = 0.5
visir_img_reduce.param.max_shift = 10.0
visir_img_reduce.param.max_mad = 0.0
visir_img_reduce.param.naverage = 1
visir_img_reduce.param.method = "xcorrelate"
visir_img_reduce.param.no_shift = False
visir_img_reduce.param.no_reject = True
visir_img_reduce.param.beampos = "NONE"
visir_img_reduce.param.eccmax = 3.0
visir_img_reduce.param.keepfrac = 0.9
visir_img_reduce.param.kappa = 5.0
visir_img_reduce.param.maxite = 3
visir_img_reduce.param.shift_beams = True
visir_img_reduce.param.error_source = "img-stdev"
visir_img_reduce.param.badimage = 0.2
visir_img_reduce.param.output_all = False
visir_img_reduce.param.extra_config = "NONE"
visir_img_reduce.param.config_fname = "/usr/share/cpl-plugins/visir-4.4.2/config/visir_default.swarp"
visir_img_reduce.param.nprocs = -1
visir_img_reduce.param.jy_val = -999.0
visir_img_reduce.param.radii = "20-20-30"
visir_img_reduce.param.delete_temp = True

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

import cpl
visir_img_reduce = cpl.Recipe("visir_img_reduce")
[...]
res = visir_img_reduce( ..., param = {"planestart":0, "planelimit":-1})

See also

cpl.Recipe for more information about the recipe object.

Bug reports

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