Here's why:

* Declination is one of the two coordinates used to specify a star's position in the celestial sphere (the other being right ascension).

* Declination measures a star's angular distance north or south of the celestial equator.

* Therefore, a star 30 degrees north of the celestial equator has a declination of +30 degrees.

Think of it like latitude on Earth. The celestial equator is like the Earth's equator, and declination is like latitude.