The muse_dark recipe



Combine several separate dark images into one master dark file and locate hot pixels.


This recipe combines several separate dark images into one master dark file. The master dark contains the combined pixel values of the raw dark exposures, with respect to the image combination method used and normalization time specified. Processing trims the raw data and records the overscan statistics, subtracts the bias (taking account of the overscan, if –overscan is not “none”) from each raw input image, converts them from adu to count, scales them according to their exposure time, and combines them using input parameters. Hot pixels are then identified using image statistics and marked in the data quality extension. The combined image is normalized to 1 hour exposure time. QC statistics are computed on the output master dark. If –model=true, a smooth polynomial model of the combined master dark is computed, created from several individual 2D polynomials to describe different features visible in MUSE dark frames. It is only advisable to use this, if the master dark is the result of at least 50 individual long dark exposures.



Create an object for the recipe muse_dark.

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



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 image 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].


Scale the individual images to a common exposure time before combining them. (bool; default: True) [default=True].


Normalize the master dark to this exposure time (in seconds). To disable normalization, set this to a negative value. (float; default: 3600.0) [default=3600.0].


Sigma level, in terms of median deviation above the median dark level, above which a pixel is detected and marked as ‘hot’. (float; default: 5.0) [default=5.0].


Model the master dark using a set of polynomials. (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_dark = cpl.Recipe("muse_dark")

muse_dark.param.nifu = 0
muse_dark.param.overscan = "vpoly"
muse_dark.param.ovscreject = "dcr"
muse_dark.param.ovscsigma = 30.0
muse_dark.param.ovscignore = 3
muse_dark.param.combine = "sigclip"
muse_dark.param.nlow = 1
muse_dark.param.nhigh = 1
muse_dark.param.nkeep = 1
muse_dark.param.lsigma = 3.0
muse_dark.param.hsigma = 3.0
muse_dark.param.scale = True
muse_dark.param.normalize = 3600.0
muse_dark.param.hotsigma = 5.0
muse_dark.param.model = False
muse_dark.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_dark = cpl.Recipe("muse_dark")
res = muse_dark( ..., 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.