Newly discovered fragments of 2,200-year-old star coordinates—once thought lost—reveal the incredible skill of the ancient astronomer Hipparchus. This colored version of a 19th-century ...

The celestial sphere is the imaginary globe around us. Ancient people believed the stars were fastened to it. credit: Holley Y. Bakich Today, I want to talk about the equatorial coordinate system.

For example, a galaxy might have a coordinate of, say, 16 hours, 34 minutes and 3.25 seconds in RA and –32 degrees, 10 minutes and 49 seconds in dec, and astronomers can use that to find it ...