Just purchased Sky Safari Pro 6 and installed it (on an iMac27 Retina and MacBook Pro 15). On both systems, the icons are missing from the setting "bar" across the top left of the screen. If you click on the (empty) box to adjust the settings, the icon appears, but then disappears when you click done. This is not the same behavior I saw in 5. Also, when I set the horizon to show Cardinal Points, they are not labeled on the iMac, though the labels (e.g., SE, S, SW....) do show on the MacBook Pro. Also, when I turn on Show Asteroids, Comets, Satellites and "with Names" the names do not appear on the iMac, though they do on the MacBook Pro. It appears that you need to test on a current model iMac 27.
Icons Missing From Setting Bar & Cardinal Points Not Labelled (Solution: Disable "Increase Contrast" In System Preferences > Accessibility > Display Panel)