Ferdinand Arsenius (active 1573-1628) was an engraver of both scientific instruments and maps. He appears to have been the son of the celebrated Louvian master, Gualterus Arsenius, with whom he made several instruments between 1573-80.
The throne comprises a central onion-shaped shield flanked by two reclining satyrs. On top of the shield is a rotating roundrel, surmounted by an interlaced strap that incorporates the shackle that holds the suspension ring. The throne is mounted on a curved bar, which is attached to the mater by means of two screws. There are three plates with stereographic projection for the following latitudes: 42º/45º, 48º/51º and 54º/57º. The rete, which is not original, is very plain and is formed along a central crossing formed by the meridian and solstitial bar. The star pointers, indicating 26 stars, are dagger-shaped. The style of engraving is varied and looks as though it has been performed by two different hands. On the back of the instrument are three concentric scales for degrees, the zodiac and the calendar. Inside these is a conversion diagram for equal-unequal hours and a shadow square. Below this is the maker's signature: 'Ferdinandus Arscenius nepos/ Gemmae Frisy Louanij fecit/ anno 1575' and within the shadow square is the name 'THOMAS * WHITSTONES', probably a former owner. This may be identified as Vice Admiral Thomas Whitestone.
Credit: National Maritime Museum, Greenwich, London. Caird Fund.