Construction and Design
The instrument is comprised of three principal rings: the outermost meridian ring, an equatorial ring, and a declination ring. The meridian ring is equipped with an adjustable connection to a suspension ring, which allows it to be clamped at different points along its latitude scale, ranging from 0 to 90 to 0. The latitude scale is divided to 10, with further subdivisions to 5 and 1.
The equatorial ring is divided into hours 0 to 12 twice, with the time subdivided to 20-minute and 4-minute intervals. A declination ring contains an adjustable pinhole that slides over a scale of months. This scale is distributed across both sides of the equatorial ring according to solar declination. When the rings are folded, the meridian and equatorial rings display an equivalent scale marked with the signs of the zodiac, each divided into six segments.
Evidence for this section
- “Three principal rings, the outermost, meridian ring having an adjustable connection to a suspension ring”
- “The equatorial ring is divided into hours 0 to 12 twice”
- “The declination ring has an adjustable pinhole moving over a scale of months”
Inscriptions and Decoration
The equatorial ring features a detailed Latin inscription: 'ALBERTO . IMPERATORIS . FILIO . IMP : FRATRI [star] ISABELL? . PHILIPPI . REGIS. FILI? . PHIL : REGIS . SORORI . ?TERNVM . REGERE . IA . D . SVCCA'. This dedication references Albert and Isabella, daughter of Philip II, who were joint rulers of the Spanish Netherlands.
Ornamentation on the declination ring includes various devices such as an eagle, the initial A, a monogram, and a pair of burning hearts. Additionally, the plate for the adjustable pinhole is decorated with depictions of the sun, moon, and stars. It bears the motto 'Simul et Semper' and a monogram of the letters 'A', 'B', 'I', 'C', and 'E', topped by a coronet.
Evidence for this section
- “The equatorial ring is engraved: 'ALBERTO . IMPERATORIS . FILIO . IMP : FRATRI [star] ISABELL? . PHILIPPI . REGIS. FILI? . PHIL : REGIS . SORORI . ?TERNVM . REGERE . IA . D . SVCCA'”
- “The declination ring is engraved with various devices and decorations, including an eagle, the initial A, the monogram and two burning hearts”
Functional Mechanism
The sundial utilizes an adjustable pinhole to cast light onto a target. This target is a pinhole located on the opposite side of the declination ring, near the intersection with the equatorial ring. The plate housing the adjustable pinhole moves within a slot in the declination ring to align with the declination scale.
On the exterior of the declination ring, an index is marked as 'LINEA HORARIA', fashioned in the form of an engraved snake and arrow. This component serves as the indicator for reading the time on the equatorial ring. Furthermore, the rim of the equatorial ring is marked at two points with the phrase 'Ante Meridiem', and the meridian ring includes markings for the dates of the equinoxes.
Evidence for this section
- “At this point there is a pinhole that acts as a target for the light passing through the adjustable pinhole”
- “On the outside of the declination ring is an index marked 'LINEA HORARIA', in the form of an engraved snake and arrow, where the time is noted on the equatorial ring”
