mFixNaN(1) Replace a particular set of values in a FITS image with NaNs (or vice-versa)


mFixNaN [-d level] [-v NaN-value] in.fits out.fits [minblank maxblank]


Converts NaNs found in the image to some other value (given by the user), or converts a range of supplied values into NaNs.


-d level
Turn on debugging to the specified level (1-3)
-v NaN-value
Value to use in place of any NaNs


Input FITS image file
Path of output FITS file. To run in "count" mode without creating an output file, use a dash ("-") for this argument.
minblank maxblank
If the "-v" switch is not used, mFixNaN will replace all pixel values between minblank and maxblank with NaN.


[struct stat="OK", rangeCount=rangeCount, nanCount=nanCount]

rangeCount is the number of pixels that were found between minblank and maxblank, if they were specified. If not (i.e., NaNs were removed and replaced with value), nanCount is the number of NaNs removed.


[struct stat="OK", rangeCount=rangeCount, nanCount=nanCount"]
No debug level given
Debug level string is invalid: level
Debug level string is invalid: level
Debug level string cannot be negative
No value given for NaN conversion
NaN conversion value string is invalid: 'NaN-value'
Invalid input file 'in.fits']
min blank value string is not a number
max blank value string is not a number
Image file in.fits missing or invalid FITS
FITS library error


A FITS image with BITPIX -64 (double-precision floating point) was generated without using NaNs; all "blank" pixels are represented by very small negative numbers. This can throw off initial attempts to display the image with a proper stretch, and does not conform to the FITS standard. To replace all those "blank" pixels with NaNs:

mFixNaN original.fits NaN.fits -4.61169e32 -4.61169e10
[struct stat="OK", rangeCount=1321, nanCount=0]

To convert those NaNs back into a single pixel value:

mFixNaN -v -4.6e32 NaN.fits blankval.fits
[struct stat="OK", rangeCount=0, nanCount=1321]


The drizzle algorithm has been implemented but has not been tested in this release.

If a header template contains carriage returns (i.e., created/modified on a Windows machine), the cfitsio library will be unable to read it properly, resulting in the error: [struct stat="ERROR", status=207, msg="illegal character in keyword"]

It is best for the background correction algorithms if the area described in the header template completely encloses all of the input images in their entirety. If parts of input images are "chopped off" by the header template, the background correction will be affected. We recommend you use an expanded header for the reprojection and background modeling steps, returning to the originally desired header size for the final coaddition. The default background matching assumes that there are no non-linear background variations in the individual images (and therefore in the overlap differences). If there is any uncertainty in this regard, it is safer to turn on the "level only" background matching (the "-l" flag in mBgModel.


2001-2015 California Institute of Technology, Pasadena, California

If your research uses Montage, please include the following acknowledgement: "This research made use of Montage. It is funded by the National Science Foundation under Grant Number ACI-1440620, and was previously funded by the National Aeronautics and Space Administration's Earth Science Technology Office, Computation Technologies Project, under Cooperative Agreement Number NCC5-626 between NASA and the California Institute of Technology."

The Montage distribution includes an adaptation of the MOPEX algorithm developed at the Spitzer Science Center.