Star Removal Aperture Tool


The StarEdit Tool is used to adjust the shape of the markers used in the Star Removal module.

The Star Edit Window makes it easy to change the marker Properties. Doing so changes the way templates and targets are measured and removed from the image.

Changing the Radius of the Apertures

 The Inner aperture specifies the region where the signal from each star is normalized to equal value. The Middle Aperture defines the region sampled for making the master template and the region actually subtracted from the targets. The Outer Aperture defines the outer limit for pixels used in subtracting the background. The background is computed using pixels between the middle and outer apertures.

Changing the Aperture Ellipticity

The control above the large round dial, changes the Ellipticity of the markers. Ellipticity is defined as E = 1 - b/a, in which b is the semiminor axis and a is the semimajor axis length. All 3 apertures have the same ellipticity, so they also change together. Setting a value of 0 makes the apertures circular.

Changing the Angle of Major Axis

The Angle dial orients the direction of the major axis of the marker. This is only useful if the Ellipticity is greater than 0, meaning that the apertures are not circular. The angle is always measured so that it increases from positive x through positive y (see Angle Measurement Definition), except that the astronomical 0 angle is taken along the y axis, which is north (up) if the image is a FITS format image displayed in the normal way.

Related Topics

Star Removal Module, Star Removal Properties, Aperture Photometry