The muse_ampl recipe



Determine the instrumental throughput from exposures taken with the pico-amplifier / photo diode readings.


This recipe combines several separate amplifier images (flat-fields with special FITS headers containing pico amplifier measurements) into one master image file and computes the instrumental throughput per IFU (and slice). Processing trims the raw data and records the overscan statistics, subtracts the bias (taking account of the overscan, if overscan is not “none”), and optionally, the dark from each raw input image, converts them from adu to count, scales them according to their exposure time, and combines them using input parameters. To compute the throughput the image is converted into a pixel table, the flux is then integrated over the given filter band, and the ratio of the expected flux (FITS header INS.AMPL2.CURR) to measured flux is taken, in the same units. If a geometry table was given as input, the relative area of the IFUs is taken into account when computing the flux per unit area. The resulting ratio is the instrument efficiency (throughput) and saved as QC parameters for the whole input image and per slice in the output pixel table.



Create an object for the recipe muse_ampl.

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



IFU to handle. If set to 0, all IFUs are processed serially. If set to -1, all IFUs are processed in parallel. (int; default: 0) [default=0].


If this is “none”, stop when detecting discrepant overscan levels (see ovscsigma), for “offset” it assumes that the mean overscan level represents the real offset in the bias levels of the exposures involved, and adjusts the data accordingly; for “vpoly”, a polynomial is fit to the vertical overscan and subtracted from the whole quadrant. (str; default: ‘vpoly’) [default=”vpoly”].


This influences how values are rejected when computing overscan statistics. Either no rejection at all (“none”), rejection using the DCR algorithm (“dcr”), or rejection using an iterative constant fit (“fit”). (str; default: ‘dcr’) [default=”dcr”].


If the deviation of mean overscan levels between a raw input image and the reference image is higher than |ovscsigma x stdev|, stop the processing. If overscan=”vpoly”, this is used as sigma rejection level for the iterative polynomial fit (the level comparison is then done afterwards with |100 x stdev| to guard against incompatible settings). Has no effect for overscan=”offset”. (float; default: 30.0) [default=30.0].


The number of pixels of the overscan adjacent to the data section of the CCD that are ignored when computing statistics or fits. (int; default: 3) [default=3].


Type of combination to use (str; default: ‘sigclip’) [default=”sigclip”].


Number of minimum pixels to reject with minmax (int; default: 1) [default=1].


Number of maximum pixels to reject with minmax (int; default: 1) [default=1].


Number of pixels to keep with minmax (int; default: 1) [default=1].


Low sigma for pixel rejection with sigclip (float; default: 3.0) [default=3.0].


High sigma for pixel rejection with sigclip (float; default: 3.0) [default=3.0].


Factor to describe the widening of the beam from the focal plane to photo diode 2. (float; default: 1.1) [default=1.1].


Lamp temperature [K] used to create the black body function. (float; default: 3200.0) [default=3200.0].


Save the processed and combined master image before any concolution is done. (bool; default: False) [default=False].


Save the table with all the processed pixel values. (bool; default: False) [default=False].


Merge output products from different IFUs into a common file. (bool; default: False) [default=False].

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

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

muse_ampl.param.nifu = 0
muse_ampl.param.overscan = "vpoly"
muse_ampl.param.ovscreject = "dcr"
muse_ampl.param.ovscsigma = 30.0
muse_ampl.param.ovscignore = 3
muse_ampl.param.combine = "sigclip"
muse_ampl.param.nlow = 1
muse_ampl.param.nhigh = 1
muse_ampl.param.nkeep = 1
muse_ampl.param.lsigma = 3.0
muse_ampl.param.hsigma = 3.0
muse_ampl.param.fbeam = 1.1
muse_ampl.param.temp = 3200.0
muse_ampl.param.savemaster = False
muse_ampl.param.savetable = False
muse_ampl.param.merge = False

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

import cpl
muse_ampl = cpl.Recipe("muse_ampl")
res = muse_ampl( ..., param = {"nifu":0, "overscan":"vpoly"})

See also

cpl.Recipe for more information about the recipe object.

Bug reports

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