Skip to main content

Ramsden's circle at Palermo, 1805

Reference Code: GBR/0180/RGO 4/181

Scope and Contents

Description by Giuseppe Piazzi of the circle made by Jesse Ramsden for the Observatory at Palermo, translated from the Italian by Margaret Maskelyne from Piazzi's, 'Della Specola Astronomica de' Regi Studi di Palermo', Libro II, capo Primo, p. 15 et seq.

1. General idea of the instrument.

2. Vertical axis.

3. The azimuth circle.

4. Supports of the vertical axis.

5. The iron circles.

6. The circle of mahogany.

7. The railing.

8. Mechanism for the circular motion of the vertical axis.

9. The microscopic micrometer of the azimuth circle.

10. The reflector of the azimuth circle.

11. The vertical circle.

12. Supports of the horizontal axis.

13. Mechanism to move the vertical circle on its own axis.

14. The upper microscopic micrometer of the vertical circle.

15. The lower microscopic micrometer of the vertical circle.

16. The plumb line.

17. Reflectors of the microscope.

18. The telescope.

19. Eye glasses.

20. Mechanism to illuminate the wires in the focus of the telescope.

21. Microscopic level.

22. The manner of fixing the first iron circle on the pavement and the four columns round it.

23. To place the vertical axis perpendicularly.

24. Adjustments of the horizontal axis.

25. To proportion the images formed by the microscopes.

26. Adjustments of the micrometer of the vertical circle.

27. Reflection of the line of collimation with respect to the horizontal axis.

28. To determine the error of the line of collimation, with respect to the vertical axis.

29. To find and correct the error which may result to the angles measured by any change which may happen to the vertical axis.

30. The divisions of the circles and the manner of reading off.

31. The errors to which the observations may be subject.

32. Advantages of the circle.


  • 1805

Conditions Governing Access

Unless restrictions apply, the collection is open for consultation by researchers using the Manuscripts Reading Room at Cambridge University Library. For further details on conditions governing access please contact Information about opening hours and obtaining a Cambridge University Library reader's ticket is available from the Library's website (


1 envelope(s) (1 envelope)

Language of Materials


Former / Other Reference


Finding aid date

2005-11-07 10:58:12+00:00

Includes index.

Repository Details

Part of the Cambridge University Library Repository

Cambridge University Library
West Road
Cambridge CB3 9DR United Kingdom