The mater consists of three layers of brass riveted together. The rim is quite large and is engraved with a scale of degrees divided by 5 and by 1, numbered from [0] to 60 by 20. All the numbers on the instrument are in Gothic script. On the same scale are numbered the hours, from 1 to 24 by 1, with 12 at the top. Further to the centre is a transversal scale divided to the degree, numbered from [0] at the nadir to 360 by 5. Each transversal is divided to 1/5 degree by 5 dots. There are no plates but the inside of the mater is engraved with unequal hour lines numbered from 1 to 12. Two series of numbers ranging from 0 to 58 are engraved corresponding to the latitude lines but in an irregular and not obvious order. The numbers are symmetrical about the meridian line. The rete has star pointers of the 'wavy flame' type for 48 stars all named in Latin. One of them is broken. The Capricorn line ends in acanthus leaves. The east-west line is counterchanged three times and there is no meridian line. The ecliptic has a scale of degrees divided to 5 and to 1 degrees, numbered by 5 from 5 to 30. The zodiacal signs are named and the final 's' is horizontal. The back of the rete has working lines of division.The back of the mater is engraved on the rim with a scale of degrees divided to the degree, numbered in four quadrants from 90 to 5 by 5 with 90 at the zenith. Further to the centre is zodiac scale divided to the degree numbered from 5 to 30. The zodiacal signs are named and the final 's' is horizontal. Further to the centre is a calendar scale divided to the day, numbered every 5 days from 5 to the final day of the month as appropriate. The names of the months are engraved on a more inner circle. The first point of Aries corresponds to the first of January. Further to the centre are three more scales. The more external one is divided in 30 parts, each subdivided to 1/3 and to 1/12, numbered from 1 to 29 by 1, starting from 30 December. The second scale is divided in hours, each subdivided in 6 and in 30 parts, numbered from 1 to 12, with also the 10th and 20th division numbered. The second scale, further to the centre, is numbered in the same way but divided differently. Further to the centre is a table of coordinates engraved 'LOCA PRINCIPAIA [sic] IN REGIONIBUS' for 112 places, with latitude 'LATITUDO' and longitude 'LONGITUDO'. 'CAFFA' does not have coordinates, and 'NORU<M>BERCA' does not have longiutude. Further to the centre is a shadow square engraved on the rim of a hollow circle. The two upper quadrants are numbered 1 to 12 ( 'VMBRA VERSA') to 1 ( 'VMBRA RECTA') each quadrant, with 1 at the top, numbered by 1. The lower quadrants are divided in degrees to the degree and numbered from 5 to 90 by 5 with 90 on the meridian line.

In the centre of the plate is an engraved hollow circle, divided in four quadrants. Three concentric circles are engraved on the top quadrants and are named the first 'EQVATOR MORE', the second 'EQVATOR VMBRE' and the third 'EQVATOR SEMIDIAMETRORVM LVNE ET UMBRE', 'EQVATOR DIVERSITATIS ASPECTVS LVNE'. The top right quadrant is divided on the rim with an unequal scale numbered from 1 to 21 and engraved 'PVCIA' (sic). The quadrant itself is divided in squares numbered on the edges from 5 to 60 by 5. The areas between approximately 23 to 28 and between 52 to the rim are divided in smaller squares. The bottom quadrants are engraved on the rim with an equal scale numbered from 1 to 5 with each unit divided into 5 and 25 parts, with the finer subdivision numbered from 10 to 50 by 10. The scale runs from the east west line to the meridian line. Further to the centre is an unequal scale divided to 5 and to 1, numbered I and II, 5, 7, 8 and 9, with the subdivisions numbered from 5 to 25 by 5. The bottom right quadrant is engraved with circles concentric to the centre of the astrolabe. The more external one is engraved 'EQVATOR PVCTORVM SOLIS', then the following 'EQVATOR SEMIDIAMETRORVM SOLIS ET LVNA', then 'CIRCVLVS DIVERSITATIS ASPECTVS SOLIS'. This circle is engraved with an unequal scale numbered from 1 to 3 with the 20th and 40th subdivisions numbered. The fourth and inner circle is engraved 'CIRCVLVS SEMIDIAMETRI SOLIS'. The bottom left quadrant is engraved with a circle named 'PVCTA ECLIPTICA SOLIS' and is numbered from 1 to 12. It is divided in squares, numbered on the edges of the quadrant from 5 to 30 by 5. The space between 31 and 35 approximately is divided into smaller squares. The lines are engraved 'MINVTA LATITVDINIS LVNE ET SEMIDIAMETRORVM' and 'MINVTA CASVS'.

In the hollow circle fits another brass disc. On one side it is engraved with a table of hours, numbered from 1 to 11, with the abbreviated names of the zodiacal signs engraved on the vertical lines. In scrollwork are the engravings 'HORA ANTE MERIDIEM' and 'HORA POST MERIDIEM'.

The back of the disc is engraved with scales on the rim. The outermost one is a calendar scale divided to the day and numbered by 5 from 10 to the last day of the month as appropriate. The names of the months are also engraved. The following scale is a calendar scale with the signs numbered from 1 to 12 starting from Aries, divided to 5 and to 1 degree, numbered from 10 to 25. The first point of Aries corresponds to the first of January. The following scale is similar to the previous one but runs clockwise instead of counterclockwise, and only Aries is named. Further to the centre is a scale of hours numbered from 1 to 12, each hour divided into 5 and into 30, with the 10th and 20th division numbered. The scale starts at the first point of Aries and the first division is engraved '10 MIN'. The following scale is numbered from 1 to 19, each part divided into 5 and 15 parts, with a remainder equivalent to about 5 units. It is indicated 'capitis' and 'IG'. The following scale is similarly divided into 9 parts, each subdivided to 2, numbered from 10 to 50 except for the second last which is numbered to 40, and it is inscribed 'IG'. The last circle is divided into 8 parts each subdivided to 2, numbered from 10 to 50 and inscribed 'IG'. The centre of the disc is engraved with spiral lines numbered from 1 to 14, an eccentric circle inscribed 'EQVATOR HORARVM' and a concentric circle divided into 12, subdivided to 1/4, numbered from 1 to 12, and engraved 'MENSES [star] ANNI'.

On the front of the instrument fits a radial rule, inscribed 'SEPTEMTRIONALI' and 'MERIDIANA' and engraved with latitude degrees to the degree, from 0 to 85 (80 on the edge of the rule) for the northern latitude, and from 0 to 23 for the southern latitude, numbered by 5. Towards the end of the rule is the date, in scrollwork, '1483'. The end of the rule is decorated.

On the back of the instrument is a counterchanged alidade with two double sights. The pin is rose-shaped and the wedge is plain.

The throne is plain and three-lobed and the strong shackle is made of three rings and a hook.