A tool to adjust data values of images by equalizing each chip’s PHOTFLAM value to a single common value so that all chips can be treated equally by AstroDrizzle.
Authors: | |
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Mihai Cara | |
License: | |
http://www.stsci.edu/resources/software_hardware/pyraf/LICENSE |
Adjust data values of images by equalizing each chip’s PHOTFLAM value to a single common value so that all chips can be treated equally by AstroDrizzle.
Parameters: | |
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files : str (Default = '*_flt.fits')
sciext : str (Default = ‘SCI’)
errext : str (Default = ‘ERR’)
ref_phot : float, None (Default = None)
ref_phot_ext : int, str, tuple, None (Default = None)
phot_kwd : str (Default = ‘PHOTFLAM’)
aux_phot_kwd : str, None, list of str (Default = ‘PHOTFNU’)
search_primary : bool (Default = True)
readonly : bool (Default = True)
clobber : bool (Default = False)
logfile : str, None (Default = ‘photeq.log’)
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Notes
By default, photeq will search for the first inverse sensitivity value (given by the header keyword specified by the phot_kwd parameter, e.g., PHOTFLAM or PHOTFNU) found in the input images and it will equalize all other images to this reference value.
It is possible to tell photeq to look for the reference inverse sensitivity value only in a specific extension of input images, e.g.: 3, (‘sci’,3), etc. This can be done by setting ref_phot_ext to a specific extension. This may be useful, for example, for WFPC2 images: WF3 chip was one of the better calibrated chips, and so, if one prefers to have inverse sensitivities equalized to the inverse sensitivity of the WF3 chip, one can set ref_phot_ext=3.
Alternatively, one can provide their own reference inverse sensitivity value to which all other images should be “equalized” through the parameter ref_phot.
Note
Default parameter values (except for files, readonly, and clobber) should be acceptable for most HST images.
Warning
If images are intended to be used with AstroDrizzle, it is recommended that sky background measurement be performed on “equalized” images as the photeq is not aware of sky user keyword in the image headers and thus it cannot correct sky values already recorded in the headers.
Examples
In most cases the default parameters should suffice:
>>> from drizzlepac import photeq
>>> photeq.photeq(files='*_flt.fits', readonly=False)
If the re-calibration needs to be done on PHOTFNU rather than PHOTFLAM, then:
>>> photeq.photeq(files='*_flt.fits', ref_phot='PHOTFNU',
... aux_phot_kwd='PHOTFLAM')
If for WFPC2 data one desires that PHOTFLAM from WF3 be used as the reference in WFPC2 images, then:
>>> photeq.photeq(files='*_flt.fits', ref_phot_ext=3) # or ('sci',3)
Print out syntax help for running skymatch
Parameters: | |
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file : str (Default = None)
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