If you look into the void while your feet position is is at one of these levels, you will see one of the following: the sun and bright sky at any level above Y=0, the moon and the night sky (without stars) at Y=0 - (approx.) Y=-1.6, and blackness at approximately Y=-1.61. Please note that, in the world that the screenshots were taken, gamerule doDaylightCycle was off and the time was set to 6000. Below are pictures of all the possible sightings and the levels that you will see them at.