Open the Aperture Tool by clicking 
on the Aperture Photometry Toolbar.
Aperture Tool
The Aperture Tool is a small floating Tool Window used to adjust the shape of the markers used in the Aperture Photometry package.
Open the Aperture Tool by clicking on the Aperture Photometry Toolbar.
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The Aperture Tool Window makes it easy to change the marker parameters. Doing so changes the amount of signal being measured through the inner aperture and affects the measurement of the local sky background between the 2 outer apertures. In the description below, the term "marker" refers to the set of 3 apertures used to mark and measure each object. |
The upper 3 edit fields show the Radius in units of pixels. Actually, this is the semimajor axis of the aperture, since Mira allows for the apertures to be elliptical. For a circular aperture, the semimajor axis equals the radius. From the top control downward, these 3 fields show 1) the inner aperture that measures the object, 2) the inner sky aperture, and 3) the outer sky aperture. Needless to say, these three apertures should have radii in increasing order.
The 4-th control, above the dial, changes the Ellipticity of the markers. All 3 apertures have the same ellipticity, so they also change together. Setting a value of 0 makes the apertures circular.
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.
The [Apply] button applies your settings if the Auto option is not checked. Since Mira updates all the measurements when the settings are applied, it is sometimes desirable to uncheck the Auto option and make all your changes before clicking [Apply] to force everything to be re-measured.
If the Auto check box at the bottom of the window is checked, releasing the mouse on any control causes Mira to recalculate all magnitudes for all images in the Image Window and then update the Photometry Measurements window. If this check box is unchecked, Mira does no recalculation until you click [Apply].
The Aperture Tool Window is a shared resource, meaning that there is only one of them and therefore, if you have more than 1 Photometry Toolbar Command going, it will have to be shared between them.
The Aperture Tool communicates with the top-most Image Window where an Aperture Photometry Toolbar is active.
If you have more than one Aperture Photometry process going, you can see the values in the Tool Window change when you click on the different windows. One useful result of this is that you can easily compare the effect of different aperture parameters by opening the same image(s) for aperture photometry in a number of separate Image Windows. Simply click on each window in turn to connect it with the Aperture Tool and then change the settings. This also shows why each Image Window is connected to a different Photometry Measurements Report window.
