The style of this portrait is particularly in line with the normal approach taken by Holbein for this genre. There is the iconography, for example, which immediately tells us of the subject's occupation. There is also the trademark facial expression that is deliberately vague, neither happy nor sad.
The element to this piece that does stand out, somewhat, is the unusually large amount of detail that Holbein puts into the background of this scene. He would normally just depict the subject holding one or two items and leave the background plain and dark. In this piece he chooses to continue the iconography right across the work, all of which ultimately tells us of the gentleman’s involvement in Astronomy.
Nikolaus Kratzer was a famous German astronomer and also shared somne mutual friends with the artist, including Sir Thomas More, whom also became a subject for the artist at a later date. In order to underline his occupation in this painting, Holbein adds a polyhedral sundial, a semi-circular star quadrant and a shepherd's dial. The most famous portrait of an Astronomer remains a work by Vermeer of the same name.