Ellipse Tool command (Tools menu)

The Ellipse Tool  can be used to determine the angular size (major and minor axis) and position angle of extended objects.

Ellipse Tool Elements

The Ellipse Tool consists of three graphical elements:

1. A red line that shows the ellipse.

2. Five rectangles that can be used to adjust position and size of the ellipse.

3. Text that shows the position angle as measured from the north celestial pole (PA) and the angular size (in arcminutes) of the ellipse's major and minor axes.

Sizing and Orienting the Ellipse

Click and drag on one of Ellipse Tools the small rectangles.

• Yellow Rectangle - Click and drag on this rectangle to change the position of the center of the ellipse.

• Green Rectangles - Click and drag on this rectangle to adjust the ellipse's position angle (PA) and the size of the major axis. The position angle and angular size of the major and minor axes are continuously updated.

• Gray Rectangles - Click and drag on this rectangle adjust the size of the ellipse's minor axis. The position angle and angular size of the major and minor axes are continuously updated. Note that the size of the minor axis cannot exceed the size of the major axis.

The color of the Ellipse Tool's rectangles may change when the ellipse is dragged over pictures of celestial objects. This is expected behavior.

Use the Ellipse Tool in conjunction with the Find command to show the size and orientation of objects on the Virtual Sky. The Ellipse tool is automatically drawn around extended objects, showing the object's size and position angle from the source catalog.