Centroid Properties

Centroid Properties control the measurement of accurate centroid positions in a image or Image Set. These properties can be changed globally, to make default settings for new image windows, or locally, to affect centroid calculations only in the specific window. The default properties dialog uses a profile control to save and recall parameter sets for use by future image windows. Local properties affect only the specific Image Window for which they are changed.

Open these dialogs using the View > Default Properties > Centroids command and the View > Local Properties > Centroids command.

Centroid Properties
Profile [\|>]	Selects the parameter profile for this command and allows you to save or work with existing presets.
Centroid on	Selects the direction of intensity profile used for calculating centroid positions. This is measured from the pixel values and is not affected by the choice of display settings, such as the palette or contrast.
Positive Points Negative Points	Selects whether to centroid on positive-going values (peaks) or negative-going values (valleys).
Sample Radius	Defines the distance from the target point within which pixel data are used to compute the centroid position. A reasonable radius value is approximately half the diameter of a point source image.
Tracking Radius	Defines the maximum distance from the current position that Mira will search in the next image to lock onto a new position. This is only used when tracking objects through an Image Set.

Choosing Sample Radius and Tracking Radius

The Sample Radius defines the distance from the target point within which points are used to compute the centroid position. A reasonable radius value is approximately half the diameter of a point source, such as a star image.

The Tracking Radius is used when computing the centroid of an Image Set. This value defines the maximum offset distance Mira will search in the next image to lock onto a new centroid position.

Note	Centroid positions are computed using image data, not the screen display. Choose Positive or Negative based upon the type of object to measure rather than the palette or other image display properties.

Choosing Sample Radius and Tracking Radius

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