Here are some other names for a clear night sky, with varying levels of formality and imagery:

Formal:

* Starry sky

* Celestial dome

* Night sky

Descriptive:

* Inky black sky

* Diamond-studded sky

* Velvet sky

* Star-strewn sky

* Azure expanse (though this usually refers to the daytime sky, it can be used poetically)

Poetic:

* The canopy of stars

* The celestial tapestry

* The infinite night

* The heavens above

Informal:

* A million stars out

* A beautiful night

* Clear as a bell

The best name will depend on the context and the specific imagery you want to evoke.