These are two canvass prints illustrating the satellites of Jupiter (Jovilabium) [Inv. MdS-149] and Saturn (Saturnilabium) [Inv. MdS-150], probably produced on the instructions of Lothar Zumbach von Koesfeld (1661-1727), musician, mathematician and lecturer in astronomy at Cologne, Leyden and Cassel. This latter, as Poggendorff records (op. cit.), wrote a series of works illustrating the production and use of planetolabiums, instruments he claimed he had invented. Particular mention should be made of a Jovilabium i.e. instrumentum astronomicum ..., of 1716 and a Saturnilabium i.e. instrumentum astronomicum ..., of 1726.
J.C. Poggendorff (1863), p. 1421.