3. Select a sub-area of the chip for real-time image updates.
When the focus window appears, indicating that you are in focus mode, the status bar in the focus window should be active as a dark frame and a full frame light image are taken. After being digitized and downloaded, the image will appear in its own window. A separate "Contrast" window will also appear. A typical full frame acquisition time is about 30 seconds.
The image should contain a donut-shaped object, a large whitish ring with a darker center ("donut hole"). The donut is the out of focus star. As the star comes into focus, the donut will decrease in size until it becomes a small white circle. Optimum focus has been reached when this circle is as small as possible.
To reach optimum focus, you will use the near real-time image update provided in "Planet" mode. This will allow you to see, almost instantaneously, the effects (on the image of the star) of turning the telescope's focus knob. This real time update is achieved by selecting a sub-area of the chip with the transparent box (outlined in white) in the image window. By choosing a smaller section of the chip, a full image frame does not need to be downloaded each time the image is updated. Image acquisition times will therefore be much faster than the regular 30 seconds. The smaller this selected sub-area is made, the quicker the download times will be.
Ideally, the sub-area that you choose can be small because a star only covers a small part of the chip. At this point, however, your donut is probably fairly large and a small box would not be helpful. You can use a medium sized box, however, by realizing that the star will come to focus at the center of the donut hole. Center the transparent box on the approximate center of the donut hole (move the box by clicking and dragging with the mouse). Then resize the box (click and drag on one of the two small squares in the top left hand and bottom right hand corners of the transparent box) so that it includes a small part of the donut's whitish ring. This will allow you to verify, in the next step, that you are turning the focus knob in the correct direction.
After positioning the box, click on the "Resume" button in the "Focus" window. Images will now be continuously downloaded and updated.