GNU Astronomy Utilities


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7.2.2.4 NoiseChisel output

The default name and directory of the outputs are explained in Automatic output. NoiseChisel’s default output (when none of the options starting with --check or the --output option are called) is one file ending with _labeled.fits. This file has the extensions listed below:

  1. A copy of the input image, a copy is placed here for the following reasons:
  2. The object/detection labels. Each pixel in the input image is given a label in this extension, the labels start from one. If the --onlydetection option is given, each large connected part of the image has one label. Without that option, this extension is going to show the labels of the objects that are found after segmentation. The total number of labels is stored as the value to the NOBJS/NDETS keyword in the header of this extension. This number is also printed in verbose mode.
  3. The clump labels when --onlydetection is not called. All the pixels in the input image that belong to a true clump are given a positive label in this extension. The detected regions that were not a clump are given a negative value to clearly identify the sky noise from the diffuse detections. The total number of clumps in this image is stored in the NCLUMPS keyword of this extension and printed in verbose output.

    If the --grownclumps option is called, or a value of 1 is given to it in any of the configuration files, then instead of the original clump regions, the grown clumps will be stored in this extension. Note that if there is only one clump (or no clumps) over a detected region, then the whole detected region is given a label of 1.

  4. The final sky value on each pixel. See Sky value for a complete explanation.
  5. Similar to the previous mesh but for the standard deviation on each pixel.

To inspect NoiseChisel’s output, you can configure SAO DS9 in your Graphic User Interface (GUI) to open NoiseChisel’s output as a multi-extension data cube. This will allow you to flip through the different extensions and visually inspect the results. This process has been described for the GNOME GUI (most common GUI in GNU/Linux operating systems) in Viewing multiextension FITS images.


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