[Astrolabium catholicum]

4 engraved circular plates pasted on wood boards, with movable attachments.
The circular discs are signed, and dated 1624, by the engraver and publisher Willem Janszoon, who dedicated the astrolabe to Adriaan Metius. The discs are incorporated in a large contemporary vellum bound case, which when closed has the appearance of a folio volume.
Plate descriptions from Koeman: plate 1) ecliptic, a disc, rotating within a graduated circle with hours and degrees, supplemented with a shadow quadrant; plate 2) geographical grid in an equatorial stereographic projection, provided with a rotating rule and slide arm with pointer; plate 3) regular astronomical astrolabe with its components: rete and limbus; plate 4) celestial sphere in stereographic polar projection with stars between 90° northern and 30° southern declination.
Koeman records signatures on all four plates (based on Hamburg, Universitätsbibliothek copy): plate 1) Delineavit et excudit Guiljelmus Janssonius Caesius Anno 1628; plate 2) Amsterodami Prostant apud Guiljelmum Caesium. A° 1624; plate 3) Clari[ssimo] docti[ssimo]q[ue] viro D[omino] Adriano Metio, Med. D. et Math. in Acad. Franequerana Professori, hoc a se delineatum Planisphaerium, in amicitiae testimonium offert Guiljel. Janssonius Caesius; plate 4) Coeli Planisphaerium describ.: Guiljelmo Janssonio Caesio Anno 1628.
Upon the tablet of Horizons is superimposed the rotable rete, or "star map" for finding the stars. The rete in this example is an unusally elaborate and finely cut-out one; the stars are represented by small gilded circles.
Metius also published a guide on how to build the astrolabe: Astrolabium, hoc est astrolabii utriusque accurata descriptio, eorundem fabricam, usumque in astronomia et geographia multiplicem complectens, Amsterdam, 1626.
Morgan copy with plates 1 and 4 without printing signatures.
Morgan copy missing limbus on plate 3 and arm on plate 4.