In 1876, he puchased an equatorially mounted 5-inch refractor from John Byrne of New York for $ 400, or about 2/3 of his annual income that year. In January, 1881, still employed at the photo studio, he married Rhoda Calvert, an England-born lady whom he knew from his work in the studio. On May 12, 1881, Barnard discovered his first comet, which however he did not announce. He found his second comet on September 17 of the same year, and another one on September 13, 1882.

In 1892, Barnard discovered Jupiter's fifth moon, Amalthea.

In 1916, he discovered the fast proper motion of more than 10 arc seconds per year, of the 9.5-magnitude star cataloged as Munich 15040 or LFT 1385 in Ophiuchus. This is the fastest proper motion found so far (even now, at the time of this writing in 2001) for any star beyond the Solar System. Since, this star is called Barnard's Star.