When can't astronauts land on the moon?

The astronauts landed in the lunar morning (remember, a full lunar day is about 29 Earth days long!) so that shadows would be long, so they could judge their approach to the ground, Dodge boulder-strewn areas, and such. Also, it would be much cooler, which is easier on the astronauts and their gear. The temperature at lunar noon can be as much s 250 F. so you can see why they went early in the day!