Harta first studied architecture at the Technical University in Vienna and went to Munich in 1905 to study painting at the academy with Hugo von Habermann. In 1908, he stayed in Paris, worked for a short time at the Vitty Academy, copied old masters in the Louvre, studied French painting and subsequently traveled to Brittany. After his return to Paris, he exhibited at the Salon d'Automne and then focused particularly on the Impressionists. In 1909, he went on a study trip to Spain and spent the winter in Vienna. In 1910 and 1911, he was in Belgium, in 1912 in Italy and in 1913 he visited Paris for the second time. From the fall of 1913 until he was called up for military service in 1916, he lived in Vienna. In 1917, he moved to Salzburg, where he remained until 1923. In 1926/27 he stayed in Paris again. In 1919, he was the founder and president of the artists' association “Der Wassermann” and from 1928 to 1935 a member of the Hagenbund. He exhibited his works in numerous exhibitions at home and abroad. In 1921, he received the Great Silver State Medal in Salzburg, in 1927 the honorary diploma from the International Exhibition in Bordeaux, in 1929 the Austrian State Prize and in 1934 the Honorary Prize of the City of Vienna.