Radial Profile Plot

The Radial Profile Plot shows the luminance of all pixels surrounding a point. Mira calculates the Full Width at Half Maximum ("FWHM") by fitting a Gaussian + Constant model to the point data. As a result of the profile fitting, the background and peak values are also reported. Properties that control the fit and calculations are set using the Radial Profile Properties dialogs.

Procedure

1. Move the center of the Image Cursor to the point at which to make the plot. If using the centroid, you need only to move the Image Cursor to within a few pixels of the target position.

2. Use the Plot > Radial Profile menu command or click the button.

The plot below was made from a weak point source.

• The Radial Profile Plot properties are configured using the Radial Profile Properties dialogs.

• If the source image has a WCS calibration, the Radial Profile can be plotted with radius in pixel units, linear distance units, or angular units on the horizontal axis. Otherwise the plot is made using pixels as the unit of radius.

After computing the FWHM value, Mira saves the value into the image header using the PSF-FWHM keyword. This value is saved in units of pixels. In addition, if you create the plot using world coordinates (see below), Mira also saves the FWHM in world coordinate units using the WCS-FWHM keyword.

Related Topics

Plotting commands, Radial Profile Properties, Plot Coordinate Systems, Plot Properties, FWHM Properties, FWHM Measurement