The dry electromagnetic chronograph is an instrument used for recording on a paper strip the instant in which the passage of a celestial body under observation on the meridian took place. The instrument essentially consists of two parts: a device for advancing the paper and a system with writing tips. Registration takes place via two arms, with points that pierce the paper, controlled by electromagnets: one connected to a clock (marks the seconds) and the other controlled by the observer using a telegraphic key (marks the instant of the astronomical phenomenon ).