You also have to sometimes be very close to the horizon to see either. I can never use the little sun controls track ball. I always overshoot. Look at the little Azimuth: and Altitude: settings. If you click on the numbers next to them you can manually change the values to move the sun. Azimuth is around the disk 360 degrees. Altitude is from edge to center 90 degrees. Sometimes you need to be 15 to 20 degrees just to see the sun disk. Click on the little yellow ball to the right of the trackball and it will change from yellow sun to blue moon and change your scene from day to night. Sun and moon are always 180 degrees apart in bryce. If you want both in the sky at once you will need a to put a moon texture on a sphere and hang it in your scene. Hope this helps!