E L Johnson, son of a medical practitioner, matriculated at Grey College, Bloemfontein and, together with his brother, started work on a mine. When his brother was killed in a mine accident he applied for a position at the Union Observatory in Johannesburg and started work as a learner astronomer in 1914. Following the outbreak of World War I (1914-1918) he served in the armed forces of the Union of South Africa during the campaign in German South West Africa (now Namibia) but fell ill and was sent home. After recovering he went to England and served as a bomber pilot in the Royal Flying Corps. After the war he returned to his post at the observatory, where he remained for the rest of his career.
Johnson worked with H E Wood* to produce star maps of the sky south of declination 19 degrees south. While photographing regions of the sky in declination 52 degrees south in January 1935 he discovered a faint comet that remained visible for less than two months. It was officially named Johnson's comet 1935. He discovered a second comet in 1948. His observations of some 30 comets were published in the Circular of the Union Observatory, Johannesburg, from 1921 to 1953.
Johnson also discovered 18 asteroids (minor planets) between August 1946 and July 1951. The most important of these was named Betulia, which he discovered on 22 May 1950 during its close approach to the earth. His observations of asteroids were also reported in the observatory's Circular during 1928-1953.
He was a member of the Astronomical Society of Southern Africa and in an article in the society's Monthly Notes in 1951 he estimated the total number of asteroids brighter than the 17th photographic magnitude to be considerably less than previous estimates.
Johnson was a man of social charm who regularly played golf. In 1922 he married Aisleen Devenish, with whom he had a daughter and a son. They lived on the observatory grounds. He retired in December 1951, but for the next few years tested potential astronomical sites with portable reflecting telescopes for the European Southern Observatory Organisation.