# Choose aperture (dialog)

The “Choose aperture” dialog is used to select an aperture. During the photometry, each object is measured using a set of predefined apertures of different sizes. The best aperture size depends on width of objects and background noise level, these parameters vary for each run.

## Selecting the aperture

The dialog for selecting an aperture

(1) The table of defined apertures is displayed here.

(2) The list of available data sets are available is shown here. Separate data sets are made for each couple of a comparison star (C) and a check star (K1, K2, etc.).

The graph of curve of deviations as a function of aperture index (3) is shown in the right part of the dialog. The point that corresponds to the currently selected aperture is highlighted.

Left click on a point in the graph selects the aperture.

Click the “OK” button (4) to save the selection.

- Usually the best aperture corresponds to the minimum of the curve.

- The matching must be applied before the matching.

- At least one comparison and one check star must be selected before the dialog is activated.

See also

Choose stars (dialog), Light curve (dialog)