Koehler was born in Gauernick (near Dresden), Germany on December 15, 1745. He was secretary of the Astronomical Society of Leipzig from 1771 to 1776. His observatory in Dresden was equipped with two Dollond achromatic refractors of 6 ft and 10 ft focal length and an 8 ft Gregorian reflector. He was a very keen observer and since 1772 he compiled a list of 20 nebulae, published in the Astronomisches Jahrbuch for 1784 by Bode. During his observations of the comet of 1779 he discovered on April 11 the galaxies M 59 and M 60 in Virgo, a few days before Messier. He discribed them as "two very small nebulae hardly visible in a 3 ft telescope; one above the other". He is also credited with the discovery of the cluster M 67 in Cancer (according to Bode this was before 1779). Köhler died at Dresden on Sept. 19, 1801.
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An early Gregorian reflector from the Count Löser (1742), who made the 8 ft for Koehler.