Complex sentence: Edvard Hugo von Zeipel (1873--1959) was a Swedish astronomer, with the specialist fields of study of celestial mechanics, astrophotography, and theoretical astrophysics.
Split into simpler sentences: Edvard Hugo von Zeipel (1873--1959) was a Swedish astronomer. His fields of study were celestial mechanics, astrophotography, and theoretical astrophysics.