How many constellations can 1 see on a clear night?

Answer 1

At any moment on a clear night, you can always see about half the sky. There are officially 88 constellations. so at that moment you can see roughly between 40 and 50 of them (or parts of them).

Answer 2

Hi. That depends on two things. How much of the sky you can see (mountains, trees, buildings in the way etc.) and how clesr the sky is. This will aid you http://www.stellarium.com/ .