Reflecting circle (Mayer and Borda)
Círculo de reflexión (Mayer y Borda)
- Date
- 1752 (Mayer); c. 1775 (Borda) · confidence medium
- Place
- Göttingen, Lower Saxony, Germany
- Credited to
- Tobias Mayer; Jean-Charles de Borda
- Field
- Movement
What it is
A reflecting instrument with a full 360° limb that allows an angle to be measured repeatedly on different parts of the circle and the errors averaged. Mayer devised it for lunar distances; Borda improved it for French expeditions.
Mayer described it in 1752 and it was published posthumously in 1767; Borda reworked it around 1775 with the maker Lenoir.
What it led to
- more precise measurement of lunar distances and angles at sea
- the repeating circle used in geodesy (Borda)
- improvement of the modern sextant