What stars can you see?
Stars that are sufficiently close to the
north celestial pole (NCP) never set. Such stars are said to be circumpolar
stars. In order to miss going below the horizon, circumpolar stars
must be as close (or closer) to the NCP as the northern
horizon is to the NCP. Since the altitude of the
NCP is the latitude of the observer's location, circumpolar stars must
be within the observers latitude of the NCP. Equivalently they must
have a declination greater than:
dec > 90°-latitude.
(In the diagram the black half-circle is the meridian which runs from
the north point on the horizon [N], through the north celestial pole [NCP],
through zenith [Z], and ends on the south point on the horizon [S]. As usual,
the altitude of the NCP is the observers latitude. CE marks the spot where
the celestial equator crosses the meridian.)
So in the case of CSB/SJU at latitude=45°, stars with dec greater than
45° are circumpolar.