His work concentrated on using photographic plates rather than direct visual studies for astronomical research.

After his graduation, he spent the summer at Yerkes Observatory as a volunteer assisting director George Ellery Hale.

From 1899 to 1903, he was an astronomer at Yerkes, where he pioneered the use of photographic methods to determine stellar parallaxes.

[1][2] Asked how to say his name, he told The Literary Digest "The name is so difficult for those who do not speak German that I am usually called sles'in-jer, to rhyme with messenger.

They had one child, Frank Wagner Schlesinger, who later directed planetariums in Philadelphia and Chicago.