Gunter's quadrant with nocturnal
Date: circa 1625
Inventory Number: 7361
Classification: Astrolabe Quadrant
Dimensions:1 x 20 x 14.7 cm (3/8 x 7 7/8 x 5 13/16 in.)
radius: 14.2 cm (5 9/16 in.)
DescriptionThis is a variant of the Gunter's quadrant with a nocturnal on the reverse. It is made of brass. Moving from the apex to the limb, the quadrant has the following components:
Plumb line with bob wrapped in leather. The bob is a replacement. Sights are on the right-hand edge of the quadrant.
Calendar scale in four bands with months labeled in English abbreviations, and divisions into days.
Arc of solar declination running 0°-23 1/2° with divisions every 1°.
Equal hours are marked from IIII-XII-VIII, subdivided by 1/2 hours. The ecliptic is divided every 1° and marked with zodiacal symbols.
Lines of azimuth are inscribed 0°-120°, every 10°.
The shadow scale is of 100 parts, divided into intervals 0-10-0. The degree scale on the limb runs 0°-90° with subdivisions every 30'.
On the reverse, there is a nocturnal marked for hours I-XII twice by 1/8 hours around the edge of a volvelle. Along the outer limb of the volvelle, running adjacent to the hour scale, there is a calendar scale. It is divided into days and monthly intervals are indicated by English initials. The center of the volvelle has figures representing six constellations.