| Instrument | : | Spiegelboog (Mirror-staff) |
| Manufacturer | : | N. de Hilster (original by J. van Breen). |
| Country of origin | : | The Netherlands (Original also) |
| Manufacturing year | : | 2005 (Original: 1660) |
After finishing the cross-staff replica I wanted to reconstruct a navigational instrument that no longer exists: the spiegelboog. The spiegelboog was invented by Joost van Breen in the 17th century. At September 25th of 1660 he patented the instrument together with a book in which he describes it (a declaration of this patent is visible as background behind this text). The instrument has similar features as the cross-staff, but uses a mirror and two vanes for observations of weak celestial bodies. Although the instrument has been used for about 100 years by Dutch navigators, none of them survived. As none are left I made this reconstruction using the information Van Breen left in his book "Stiermans Gemack", which he published back in 1662.
After a year of research, building the instrument took me about two months. Now the instrument should be a 95% accurate reconstruction of the original. In total two reconstructions were made, the second of which (instrument no. 2) now is in the collection of the Netherlands Maritime Museum, Amsterdam (inv.no. 2008.0299). On the 22nd of October 2005 I finally presented a paper on the Reconstruction of the spiegelboog at the 'Who needs scientific instruments?' conference at museum Boerhaave in Leiden, The Netherlands. In September 2006 an in-depth article on the spiegelboog was published in the Bulletin of the Scientific Instruments Society.
Materials used on this reproduction are ebony for the staff and pear wood for the vanes. In addition to that glass, copper and brass are used for the mirror, mirror-frame, pins and springs.
I'm very grateful to Diederick Wildeman and Willem Mörzer Bruyns (both Scheepvaartmuseum Amsterdam) and Klaus Staubermann (Universiteitsmuseum van Utrecht), as they supply me with lots of information on this instrument and other contemporary instruments. I also wish to thank the Zeeland archive (Toon Franken), the National Archive, the National Library of the Netherlands and the Library of the University of Leiden for helping me out on my historic research.
In addition to that I wish to thank Cathrien Steenbeek who did a splendid job on engraving the mirrors.
Want to know if your staff belongs to a spiegelboog or cross-staff (and if it is a cross-staff you can check if the vanes are right)? You can check it yourself here.
If you like to know more, don't hesitate to contact me.