Octant of Goater (Spiegel-Oktant, 1770)

The frame and the alhidade of the octant are made of rosewood (possibly mahogany), the inlaid section is made of Indian boxwood. All other parts are made of brass. The sub-circle is divided from 0° to 90° in intervals of 20'. Its diameter is 900 mm. With the help of a transverse division, two minutes can be read directly. The instrument is set up in such a way that measurements can also be carried out with the sun in the back. The three retractable filters are reversible for this purpose. The measurement results are recorded on the ivory tablet with the pencil stuck in the middle bridge.该八分仪的框架与照准器（alhidade）采用红木（或为桃花心木）制成，镶嵌饰件选用印度黄杨木制作，其余所有部件均由黄铜加工而成。其副刻度盘的分度范围为0°至90°，分度间隔为20角分，盘面直径达900毫米。通过横向分度结构，可直接读取2角分的测量值。该仪器设计支持背对太阳时进行观测，为此配备的三块可伸缩滤光片均为可逆式结构。测量结果可通过插在中间桥座上的铅笔，记录于象牙制记录板之上。