This instrument is on display at the land office at "Pioneer Village" in Minden, Nebraska. It is identified on a card beside it as a "Surveyor's Transit".
Got to be some sort of astronomic instrument, I'd think. Looks like it's recreating declination and hour angle like a solar transit/compass.
the periscope adapter for the top scope suggests it'd be pointed to the sky. The other scope has me thinking it would point to North perhaps once the top scope is sighted at the celestial target.
by the way. thanks a lot. I didn't even know one existed 5 minutes ago. now I want one. 🙂
> ... now I want one. 🙂
Me too! 😉
Wonder what era its from.
I did a close up and can't see any identification at all. The other possibility is an alidade with an additional geodetic attachment. But don't quote me on that!
Home made solar compass?
[sarcasm]Looks like your next "Basis of Bearing" to me.[/sarcasm] 😀
I agree, would be a great piece to own.
It is clearly some attempt at a solar instrument. Are there any markings or names on it?
Looks like one of those made in India things that you can find on eBay being sold as "Vintage Surveyor's Transit" that is really nothing more than a fancy paperweight or doorstop, and was manufactured and antiqued by some chemical process just a few weeks before appearing on eBay.
But then again, it might be something genuine. I just can't wrap my head around any practicality in the placement of the scopes or the purpose of the triangle sticking up off the tilted plate and circle.
The triangle shaped thing would be the declination arc. It rotates around the circle for the hour angle (time). And the tilting circle would be for the latitude setting. These are all educated guesses without seeing the instrument.
I see the vernier window for the horizontal circle.
I have seen quite a few different style instruments with the lower telescope.
The other tubular thing is probably for sighting the sun after all the settings are made to orient true north.
It looks like a very early astronomical theodolite.
J. Penry-
This appears to be an early 1800's "Repetition Circle", with a vertical arc for determining small vertical angles. A similar instrument appears online in the Smithsonian's collection of scientific instrument maker catalogs, from the French Firm "Chevalier", dated to 1835-1860. I don't think any US-based manufacturer produced any of these, but it would take more photos to determine method of construction. Origination of this type of instrument dates to around 1780; the use of repetitive measurements was done to hopefully average out error in observation (the use of Dividing Engines for small-sized instrument circles, and/ or vernier scaling had not been widely implemented in smaller instruments yet) Documentation indicates the first commercially produced repetition circle was produced by the French firm of E. Lenoir based on the design of engineer J.C. Borda, which became known as "Borda's repetition circle".
From the description of one of his instruments in the Greek Museum of Scientific Instruments, at Hellenic Museum - JC Borda repetition circle
Jean-Charles de Borda (1733-1799), navigator and astronomer designed the repetition circle for geodesy and astronomical measurements. This instrument permits to repeat several times the same observation without returning to zero, thus the measuring errors are divided by the number of observations. This circle was probably been used by the French cartography mission in Peloponnesus during 1829-1831, lead by the Officers of the French Army Peytier, Puillon de Bollaye and Servie
*this is the same instrument featured in the American Surveyor magazine, Jan-Feb 2005 edition, linked below- the pertinent image is on pg2, as shown here:
Although they could be used for navigation and some coarse astronomical surveying,
I don't think repetition circles would have found an application in the more precise geodetic surveying, as the methods of longitude/latitude determination of the time required zenith-meridian angle measurements, which would have required vertical measurements near zenith/90°.
Smithsonian catalog of early scientific instruments- Chevalier
(you can page back/forward to see other similar instruments from Chevalier)
CONSTRUCTION OF THE REPETITION CIRCLE
The repetition circle is an invention of Etienne Lenoir (1744-1822), who was France's premier instrument-maker. The circle carries two telescopes that serve as simultaneous sights to two points between which one takes the angular distance. The instrument is known however as `Borda's repetition circle', because the instrument allows to apply a repetition of measurements for obtaining a specified degree of precision according to the method developed by Jean-Charles Borda (1733-1799), veteran naval commander and France's leading experimental physicist. The origin of Borda's repetition method originates from an idea in 1752 of the German surveyor and astronomer Tobie Mayer. The repetition method is explained in another side bar.
Lenoir constructed the first specimen of his repetition circle in 1784 under supervision of Jean-Charles Borda (17331799), veteran naval commander and leading experimental physicist. He realised the instrument in view of triangulations across the Dover Channel in 1788 for connecting the astronomical observatories in Greenwich in England and Paris in France. In its usage, Lenoir's circle proved to be an instrument comparable, if not superior, to the English theodolite of Ramsden. Based on this success, the French government ordered Lenoir to build the instruments for the French meridian expedition executed by Méchain and Delambre.
The instrument measures 76 cm (30") in height, 40 cm (16") in width and 56 cm (22") in length. It weighs 20 kg (44 pounds). Materials used for the construction are wood, iron, ivory, brass and glass.
MEASURING ANGLES BY REPETITION
Behind the construction of the repetition circle is an idea of the German surveyor and astronomer Tobie Mayer. He imagined around 1752 repeating the same observation several times without returning to zero on the circle. Finally the accumulated angle has to be divided by the number of repetitions. The resulting angle is far more precise than a single interpolation of the circle's graduation allows. An additional advantage of this method is a decrease of uncertainties that are inherent to any angle-measurement. Errors due to the instrument itself, such as irregularities in the graduation of the circle, have less influence on the result. The method is specifically effective when an instrument can be aimed with a better angular precision than a single interpolation of the circle's graduation can provide. This problem occurs when an optical telescope is used instead of an ordinary sight.
Unlike a theodolite, a repetition circle has only one circle, as explained in another side bar. The instrument's construction therefore excludes the direct measurement of horizontal angles. Before an angle between two targets can be measured, the circle must be oriented parallel to the inclined plane through the instrument's station (C) and the positions of two targets (G) and (D); see Fig. 1. For measuring zenith angles, the circle is oriented in a vertical position. One of the two telescopes (MN) is accurately leveled to provide a reference perpendicular to zenith (Z). The other telescope (AB) is aimed at the celestial body (S) for which the zenith angle has to be measured; see Fig. 9.
This is an American solar instrument. Some of the functions are similar to a repeating circle, but it differs considerably. The instrument was designed to find, by solar observations, a true meridian, and, to be able to accurately determine magnetic variation at any particular station.
The instrument appears to date from the mid 19th century, 1840s to 50s. It may be from the shop of William J. Young, in Philadelphia, or one of the Detriot makers, Grant, Crosman or Burt.
The oversize polar circle, and solar declination arc, as well as the telescope on the polar circle, suggest this is quite early and possibly experimental. The watch telescope (below) was used to run lines once the meridian was found.
J. Penry,
Dave Ingram and Dale Beeks are correct. This is a special and unique type of Solar Compass. It was made by Wm. Young for Wm. Burt in 1850. Burt called it an 'astronomical compass.' It should have Wm Young and Phil on the top somewhere as that's where Young placed them on the standard SC.
The arcs and hour circle are larger than those of a standard Solar Compass. The Michigan Society of Professional Surveyors Institute published a book written by Robert Miller on the development and history of the SC and the collaboration between Burt and Young. He spent about 25 years researching the material. The book sells for $35. Mr. Miller also wanted his research material included so we put it on a CD which is included with it.
Mr. Miller explains what he learned of its construction, etc., but was not able to learn the location of this instrument until recently. There is a good amount of detail considering Mr. Miller did not have the instrument to look at. He also gives an indication of where it was used for running a state line.
The level vials definitely look larger than those of the standard SC. As noted, the arcs and hour circle are all larger than the standard SC. The angle of view of the picture isn't good for some details but it looks like the viewing lens is mounted over a 45 degree prism at the near end of the telescope. There would have to be a shaded or dark glass since it appears that one would directly view the Sun with this instrument. This is one detail not known without seeing the instrument. With the standard SC the image of the sun was projected thru a small lens onto an image plate, as designed so as not needing to be directly viewed by eye to operate the instrument.
