Born in Hitdorf am Rhein, he studied at the University of Bonn receiving his doctorate in 1901 under Friedrich Küstner.
[1] He worked from 1901 at the Royal Observatory of Berlin and studied variable stars and specifically Mira.
As Berlin expanded, it became less possible to conduct astronomical observations there and Guthnick used, from 1906 onwards, the local park known as Babelsberg.
After the seizure of power by the Nazis in 1933, Guthnick adapted himself to new conditions under the regime, although he opposed the Welteislehre theories that were favored by Himmler.
His obituary in the Monthly Notices of the Royal Astonomical Society states he was an ardent Catholic.