NavList:

I am interested in the use of the Circles of reflection at sea.

Any information would be welcoming

Mendoza y Ríos in his “Tratado de Navegación, 1787” published a description of the Circle of reflection, (see circulo de reflexion.jpg). And Borda do the same in the same year.

The National Maritime Museum says: Reflecting Circle - Navigational/surveying instrument for angle-measurement. It works on the principle of double reflection, like the octant (q.v.) and sextant (q.v.), to measure the angular distance between two bodies by bringing the reflected image of one object alongside that of the other viewed directly. The German astronomer, Tobias Meyer (1723-62) invented the reflecting circle in the 1750s as an instrument for measuring lunar distances (the angular distance between the moon and a star) for the calculation of longitude at sea. The reflecting circle was more popular in the French and German navies than in Britain, although some British makers did produce them. The instrument is also known as the Borda circle, after the French mathematician and naval officer Chevalier Jean-Charles de Borda, who published a description in 1787.

One curiosity:

I have read that there is a portrait of Joseph Banks at the Royal Society meeting room. Mendoza y Ríos order it to Thomas Phillips, and gave it to his friend Banks, lately banks order to the painter to include an image of an offprint of the Mendoza’s work about the reflecting circle.

I have tried to find this picture on the net, but nothing,… Does anyone have any information about it??

References:

·         On an improved Reflecting Circle. Mendoza y Ríos. http://rstl.royalsocietypublishing.org/content/91/363.full.pdf+html

·         The New American Practical Navigator - http://books.google.es/books?id=EVSgAAAAMAAJ&pg=PA98&lpg=PA98&dq=circle+of+reflection+navigation&source=bl&ots=mDTD5AFcst&sig=bGBM81c02luRoCdAIwfJCtwvMM4&hl=es&ei=EtCwSbkOpMSMB-isqe0F&sa=X&oi=book_result&resnum=1&ct=result

·         Celestial navigation Reflecting circle - National Maritime Museum. UK. http://www.nmm.ac.uk/collections/search/listResults.cfm?category=90490&name=Reflecting%20circle&sortBy=title

·         Smithsonian http://americanhistory.si.edu/collections/navigation/type.cfm?typeid=5

Andrés Ruiz

Navigational Algorithms

http://www.geocities.com/andresruizgonzalez