Plot Light Curve

When an image set is measured using the Aperture Photometry package, this command is used to generate a light curve showing the variation in magnitude versus time. The target objects, standard stars, and check stars are selected according to their value in the Index column of the measurements grid. The plotted variables and error bar quantities are similarly selected from specific column titles in the measurements grid.

The Plot Light Curve command opens from the button on the Aperture Photometry Toolbar. On the dialog, click Plot to generate the light curve.

The values plotted are taken from data in the photometry results grid (the Apphot Pane or the related Photometry Measurements report window). The Object Numbers to Plot fields correspond to numbers in the "Index" column of the measurements grid. As shown above, they are entered as hyphen-separated ranges, separated by commas. In this example, the Targets are objects with index 1 and all objects with index in the range 3 through 9.

The light curves are displayed in a Plot Window that looks generally like those below. The markers, colors, and trend lines for each group can be adjusted using the button to open the Plot Marker Properties dialog. After the light curve is plotted, the scaling, background colors, and other plot characteristics can be changed using the Plot Properties and Plot Series Pane commands. Each star's light curve is assigned to a separate plot series. The Plot Animation Bar is used to show each light curve selarately or overlayed on the same plot.

Examples

The window below shows a single standard star plotted with error bars. This light curve was produced by measuring an image set using the settings shown in the dialog box above.

The two plots below show multiple targets, standards, and a check star. In the upper plot, notice that, because of the magnitude spread, the error bars do not appear even though the option to plot error bars was checked. In the lower plot, the button was used to zoom in on one of the standard stars. The following symbols have these meanings: Black squares: Target Stars; Blue diamonds: Standard Stars; Red line: a Check Star with error bars.

Notice that the top-most light curve for a target star has a marker that was changed to an open square after the plot was created, using the Plot Series Pane tool. The small vertical line inside the open square shows the magnitude error bars.

The error bars for other points can be seen by enlarging the point. The plot below shows an enlarged view around the faintest standard star shown in the above plot.

Properties

The light curve is generated from Properties you enter into the Plot Light Curve Dialog. Objects to be plotted are specified using their Object number from the Apphot Pane To plot multiple objects, you can enter numbers separated by commas, like this: 1,2,5,12 or enter a sequence of numbers like this: 1-10. You can also mix the two formats, like this: 1,2,5,8-16,24.

Plot Light Curve Properties

Targets	To plot Target Stars, check this box and enter their Object numbers from the photometry measurements grid.
Standards	To plot Standard Stars, check this box and enter their Object numbers from the photometry measurements grid.
Check Stars	To plot Check Stars, check this box and enter their Object numbers from the photometry measurements grid. A check star may be selected from among any of the target or standard stars measured.
	Click this button to open the Plot Marker Properties dialog. This command is used to specify the details of the marker used to plot the targets, standards, and check stars.
Plot Caption	Enter the caption that appears above the plot box in plot overlay mode (see the Plot Animation Bar). You can enter new text or select a previously used caption by selecting it from the drop list.
X Axis Variable	Choose the time variable to be used for the horizontal axis. The options are Time (hours), Time (minutes), and Julian Date. The Julian date will have a date offset if that is also listed in the photometry measurements table.
Y Axis Variable	Choose the measurement to be plotted. The options are Mag (the measured magnitude of the object), Mag Std (the magnitude entered for a standard star), or Net Counts.
Y Axis Error Bars	Check this box to plot error bars with the brightness measurements. Choose Error to use the measured magnitude errors or choose Error(T) to use the theoretical magnitude errors.

Examples

Properties

Related Topics