Term: declination (dec)
Declination is like latitude. It reports how far a star is from the celestial equator.
Stars closer to the north celestial pole than the south celestial pole are
said to be "above" the celestial equator, and have positive declinations.
Stars closer to the south celestial pole than the north are said to be "below"
the celestial equator. They have negative declinations. The celestial equator
itself has declination 0°. The north celestial pole has declination
+90°. It doesn't show on the SC001 as the SC001 includes only as far
north as dec=60° and as far south as dec=-60°. The red lines
below connect points that all have the same declination. (Of course,
the red lines are examples of diurnal circles.)
So on the Mercator projection of the globe the parallels of latitude
run side to side and connect points of the same latitude. On the SC001
diurnal circles run side to side and connect points with the same declination.
Latitude runs from +90° at the north pole, to 0° on the equator, to
-90° at the south pole, and it's basically the same for declination.
(FYI: the latitude here at CSB/SJU is about 45°.)
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