Declination

Declination (Dec, δ) is the celestial coordinate that measures how far north or south a star or other celestial object appears from the celestial equator—an imaginary circle in the sky directly above Earth's equator. Think of it as latitude for the heavens! Just like Earth's latitude system, declination ranges from +90° (at the north celestial pole) to -90° (at the south celestial pole), with 0° marking the celestial equator.</p><p>For example, Polaris (the North Star) has a declination of approximately +89°, placing it very close to the north celestial pole, which is why it appears nearly stationary in our northern sky. The bright star Sirius has a declination of about -17°, meaning it sits 17 degrees south of the celestial equator. Meanwhile, stars along the celestial equator, like those in the constellation Orion's belt, have declinations near 0°.</p><p>This coordinate system, developed by ancient Greek astronomers like Hipparchus around 150 BCE, remains fundamental to modern astronomy. Declination works alongside right ascension (celestial longitude) to pinpoint any object's exact position in the sky. Unlike altitude and azimuth, which change based on your location and time, declination stays constant for each star, making it invaluable for telescope pointing, star charts, and astronomical catalogs worldwide.