{"product_id":"backstaff-f6842-002","title":"Backstaff","description":"Ivory frame, sight vane and horizon vane, brass rivets. Signed on the upper arm 'Thomas Tuttell Charing X Londoni fecit', on the back of the 25 arc 'Fait par Tho:Tuttell Ingenieur de sa MajestÔòáBritanique pour les Instruments Mathematiques a Londres'. The transversal scale on the 25 arc is from 0-30 by 10' (and from 90-60), reading to 1'. The 60 arc is from 0-60 by 1. Radius of the 25 arc is 229 mm, that of the 60 arc is 686 mm. The sight vane and shadow vane slide in grooves cut in the outer edge of the arcs. Overall length of the instrument is 689 mm. Flower-pattern decorations are found on all parts of the instrument's frame. Unlike most known English back staffs, this example does not have an additional scale for the sun's semi-diameter on the 25 arc. This back staff is part of a presentation set also including a cross-staff and Gunter's scale, all fitted into a lyre case. The shadow vane is a modern replacement.\u003cbr\u003e\u003cbr\u003eThe back staff was one of the principal instruments of navigation until the development of the Octant in the 1730s. It was used facing away from the Sun and required the measurement of a shadow cast onto the degree scale. They are usually made of wood but this very rare example is made from highly decorated ivory. It was part of a gentleman's presentation set and would not have been used on board ship. The inscription suggests the original owner was French and is a complementary piece to NAV0505.\u003cbr\u003e\u003cbr\u003ePresented by Sir James Caird in 1938; purchased through Maggs Brothers from the Rufford Abbey sale at Ollerton, Nottinghamshire, by Knight, Frank and Rutley, in conjunction with Christie, Manson and Woods, October 1938.\u003cbr\u003eThomas Tuttell","brand":"prodigi","offers":[{"title":"Fine art poster \/ XS: 25 x 20cm \/ none","offer_id":57029160206718,"sku":"GLOBAL-FAP-8X10","price":22.95,"currency_code":"GBP","in_stock":true},{"title":"Fine art poster \/ S: 30 x 25cm \/ none","offer_id":57029160239486,"sku":"GLOBAL-FAP-10X12","price":28.95,"currency_code":"GBP","in_stock":true},{"title":"Fine art poster \/ M: 50 x 40cm \/ none","offer_id":1748939636780,"sku":"GLOBAL-FAP-16X20","price":38.95,"currency_code":"GBP","in_stock":true},{"title":"Fine art poster \/ L: 75 x 60cm \/ none","offer_id":57029160272254,"sku":"GLOBAL-FAP-24X30","price":54.95,"currency_code":"GBP","in_stock":true},{"title":"Fine art poster \/ XL: 100 x 80cm \/ none","offer_id":57029160305022,"sku":"GLOBAL-FAP-32X40","price":69.95,"currency_code":"GBP","in_stock":true},{"title":"Fine art poster \/ XXL: 127 x 100cm \/ none","offer_id":57029160337790,"sku":"GLOBAL-FAP-40X50","price":82.95,"currency_code":"GBP","in_stock":true},{"title":"Framed picture \/ S: 36 x 28cm \/ none","offer_id":57029160370558,"sku":"MUS-CFPM-11X14","price":59.95,"currency_code":"GBP","in_stock":true},{"title":"Framed picture \/ M: 50 x 40cm \/ none","offer_id":1748939997228,"sku":"MUS-CFPM-16X20","price":79.95,"currency_code":"GBP","in_stock":true},{"title":"Framed picture \/ L: 80 x 60cm \/ none","offer_id":57029160403326,"sku":"MUS-CFPM-24X32","price":119.95,"currency_code":"GBP","in_stock":true},{"title":"Framed picture \/ XL: 100 x 75cm \/ none","offer_id":57029160436094,"sku":"MUS-CFPM-30X40","price":159.95,"currency_code":"GBP","in_stock":true},{"title":"Postcard \/ Standard: 6 x 4in \/ Single","offer_id":57029160468862,"sku":"GLOBAL-POST-MOH-6X4","price":1.95,"currency_code":"GBP","in_stock":true},{"title":"Postcard \/ Standard: 6 x 4in \/ 10-pack","offer_id":57029160501630,"sku":"GLOBAL-POST-MOH-6X4-10","price":14.95,"currency_code":"GBP","in_stock":true},{"title":"Postcard \/ Standard: 6 x 4in \/ 20-pack","offer_id":57029160534398,"sku":"GLOBAL-POST-MOH-6X4-20","price":24.95,"currency_code":"GBP","in_stock":true},{"title":"Postcard \/ Large: 7 x 5in \/ Single","offer_id":57029160567166,"sku":"GLOBAL-POST-MOH-7X5","price":2.95,"currency_code":"GBP","in_stock":true},{"title":"Postcard \/ Large: 7 x 5in \/ 10-pack","offer_id":57029160599934,"sku":"GLOBAL-POST-MOH-7X5-10","price":19.95,"currency_code":"GBP","in_stock":true},{"title":"Postcard \/ Large: 7 x 5in \/ 20-pack","offer_id":57029160632702,"sku":"GLOBAL-POST-MOH-7X5-20","price":29.95,"currency_code":"GBP","in_stock":true},{"title":"Greetings card \/ Standard: 6 x 4in \/ Single","offer_id":57029160665470,"sku":"GLOBAL-GRE-MOH-6X4-BLA","price":2.5,"currency_code":"GBP","in_stock":true},{"title":"Greetings card \/ Standard: 6 x 4in \/ 10-pack","offer_id":57029160698238,"sku":"GLOBAL-GRE-MOH-6X4-BLA-10","price":15.95,"currency_code":"GBP","in_stock":true},{"title":"Greetings card \/ Standard: 6 x 4in \/ 20-pack","offer_id":57029160731006,"sku":"GLOBAL-GRE-MOH-6X4-BLA-20","price":26.95,"currency_code":"GBP","in_stock":true},{"title":"Greetings card \/ Large: 7 x 5in \/ Single","offer_id":57029160763774,"sku":"GLOBAL-GRE-MOH-7X5-BLA","price":3.5,"currency_code":"GBP","in_stock":true},{"title":"Greetings card \/ Large: 7 x 5in \/ 10-pack","offer_id":57029160796542,"sku":"GLOBAL-GRE-MOH-7X5-BLA-10","price":19.95,"currency_code":"GBP","in_stock":true},{"title":"Greetings card \/ Large: 7 x 5in \/ 20-pack","offer_id":57029160829310,"sku":"GLOBAL-GRE-MOH-7X5-BLA-20","price":33.95,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/2785\/2654\/files\/f6842-002.jpg?v=1772721637","url":"https:\/\/prints.rmg.co.uk\/products\/backstaff-f6842-002","provider":"Royal Museums Greenwich prints","version":"1.0","type":"link"}