back-staff and case

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Project by tallshipsailor posted 01-22-2015 07:28 AM 1509 views 1 time favorited 9 comments Add to Favorites Watch

Invented by Capt. John Davis Around 1594, the back staff was a more accurate and easier instrument to use then the cross-staff. The back staff was used for nearly 200 yrs.

To use;
The larger arch has a sight vain, that you sight the horizon from the vain through a slot in the horizon block located at the opposite end of the staff. With the sun behind you, you then adjust the shadow vain on the smaller arch until it casts a shadow onto the horizon vain precisely where the horizon has been sighted. You then add the degrees from both arch’s and use the total degrees to calculate the angle of the object off the horizon, and that number to calculate your latitude.

The Case;
One of the museum back-staffs I found was in an original case. From the photograph I was able to reproduce the case, excluding the hinges and clasps.

9 comments so far

View Greg Guarino's profile

Greg Guarino

50 posts in 947 days

#1 posted 01-22-2015 11:56 AM

I’m always fascinated by the wide variety of things people choose to build, including some I’ve never even heard of. Beautiful and precise work. Good job.


View shipwright's profile


7080 posts in 2216 days

#2 posted 01-22-2015 02:29 PM

These are both just wonderful pieces. Your time and effort in researching them was definitely worth it.
A couple of questions.
How big are they (cross staff as well)?
Are they for your personal nautical collection or will they be on display in a maritime museum somewhere?
Personally I think they would be great mantle art in any sailor’s home.

I applaud your efforts.

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fibreglass trees.

View HillbillyShooter's profile


5811 posts in 1710 days

#3 posted 01-22-2015 03:57 PM

Very interesting story and beautiful craftsmanship! Thanks for sharing.

-- John C. -- "Firearms are second only to the Constitution in importance; they are the peoples' liberty's teeth." George Washington

View PaulDoug's profile


1074 posts in 1121 days

#4 posted 01-22-2015 04:13 PM

That is a beautiful piece. Thanks for the education. Great work as are your other projects.

-- “We all die. The goal isn't to live forever; the goal is to create something that will.” - Chuck Palahniuk

View LesB's profile


1228 posts in 2861 days

#5 posted 01-22-2015 06:00 PM

Something new. Great job.

-- Les B, Oregon

View Mean_Dean's profile


4930 posts in 2565 days

#6 posted 01-22-2015 11:10 PM

That’s a beautiful navigational tool! It could serve as a backup if GPS fails!

-- Dean

View tallshipsailor's profile


19 posts in 1195 days

#7 posted 01-23-2015 01:18 AM

Thanks you guys for your comments, really makes me feel awesome coming from such talented people like yourselves. Dean, totally jealous of your new router station! I’d never come out of my shop if I had such a station!

View Sylvain's profile


638 posts in 1917 days

#8 posted 01-23-2015 03:51 PM

Could you please make a little sketch about how it is used?
(position of the eye, horizon and sun)

English is not my mother language and altough I have read your explanation several time, I still don’t undertstand.
Thank you in advance.

-- Sylvain, Brussels, Belgium, Europe - The more I learn, the more there is to learn

View tallshipsailor's profile


19 posts in 1195 days

#9 posted 02-27-2015 12:34 AM

Hi, sorry for my absence in replying to all your fantastic comments. These pieces will be in my personal collections of navigational tools and history. When I check out of this world, they will be donated to a reputable maritime museum.

I’ll try to find a few sketch depicting how each instrument is used. will post as soon as I find them.

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