Select a circle around the central point source

• select cursor and circle. When in the image window, the mouse now has a box shape with an arrow at the upper left corner. The mouse buttons act as follows:

  LEFT - to move the center of the circle at the position of the arrow point.

  MIDDLE - to size the circle.

  RIGHT - idle.

• center the circle at the point source by positioning the arrow point and clicking on the LEFT mouse button. A circle will appear at the arrow position. A verbose display will also appear in the window from which SAOimage was initiated, giving the center coordinates and radius of the circle.
• size the circle by holding the MIDDLE button and dragging the mouse until the desired size is obtained. Releasing it will fix the size of the circle at the value printed in the output window.
• save the results (in memory) by typing `s' while the mouse is in the display window. The center position and the outermost radial distance along the minor axis will be displayed if the button options cursor, region, view and cursor, region, label are ON.
• select region and write, to write the saved regions into a file for later use. Another small window will appear, with a filename saoimage.reg (default). Either hit carriage return for approval, or delete and type a new name. The file will be written in the directory from which SAOimage was initiated, unless specified otherwise in the filename.

The following text will be written to the specified file:

     # xdata$rp110590_iml.imh - XRT/PSPC PSF AR LAC
     # Thu Jul 25 11:20:17 1991
     # shape x, y, [x dimension, y dimension], [angle]
      CIRCLE(232,313,10.00)

The circle has a radius of 10.00 pixels.

• Select region and read to display this or other regions by reading them from the specified file.