To display the Herschel Focal Plane to scale, go to the Overlays menu in the main HSpot menu bar and select "Herschel Focal Plane." The focal plane to scale will appear on your image. Clicking the left mouse button at a position on the image will re-centre the focal plane at the click point. Note the cluster of mini icons labelled "Herschel" ****that have appeared on the right of the image window (Figure 19.8, “Display of the Herschel Focal Plane”). The box with the number in it shows the position angle of the focal plane. The focal plane is generated at a default position angle of 0.0 degrees. To visualise the focal plane on a particular date, use the Visibility/Orientation capability in the HSpot target entry window (the bulls-eye symbol on the HSpot main menu bar). Enter your moving target and determine the position angle for the Herschel focal plane on the date you want to observe your target. You can then enter that position angle into the box in the "Herschel" layer control to re-orient the focal plane display. In the example in the figure, a position angle of 035 degrees has been entered.
The focal plane configuration icon in the "Herschel" layer allows you to toggle apertures on and off and change the colour of the displayed apertures. See the Herschel Observer's Manual for a full description of the apertures on the focal plane. The arrow pointing to the Sun symbol in the focal plane display denotes the Herschel-Sun direction, as projected on the sky.