Pendulum Astrolabe

Title

Pendulum Astrolabe

Subject

Astronomical measurements: Astronomy

Description

Physical Description: The instrument is situated on a gray base that is 34 cm long x 21.5 cm across x 1cm high. The object is able to rotate on this base to make the viewing of objects easier. The instrument consists of two eyepieces and two lenses, one set being larger than the other. The lens and eyepieces form a near right angle. When viewed from the side, the device looks like two black check marks, one large and one small. The device is 48cm high (top of base to the top of the eyepiece), 32 cm long (tip of lense to the tip of eyepiece), and 21 cm across. The lens are 7.5 cm across and 4.5 cm across each. There are some inscriptions near the base that denote the name of the device, maker of the devices, city and state, and some serial numbers. At first glance, the object looks like a microscope, however rather than looking into a slide or something similar, the thing the observer is viewing is being reflected from the other end of the lens into the eyepiece using a mirror suspended inside the instrument.

Functional Description: First, place your eye near the eyepiece and look into it. After looking into the eyepiece, align the reticle in the eyepiece with the astronomical body that you are measuring. When the reticle and the body are aligned, this means that the body is at an altitude of 60 degrees. The light that enters the lens is then reflected into the eyepiece using a mirror that is suspended inside the instrument.

The name "pendulum astrolabe" may seem strange at first becasue the device neither looks like a typical astrolabe nor does it appear to have a pendulum located on or in the device. However, an astrolabe is simply a device used to measure the altitudes of astronomical bodies. Also, the mirror located inside the device is suspended in a pendulum-like fashion.

The actual measurement of 60 degrees seems unimportant other than that it is known that the angle is in fact 60 degrees. This can used to determiniation the declination of an astornomical body. If one measures every time that body crosses the 60 degree mark, then they could make a more educated statment about the motion of that body (period of its revolutions, etc.).

Creator

Johnathan Jaehnig, Joachim Wright, Ben Denys, and Paul Bahle

Date

1952

Language

English

Type

Physical Object

Identifier

M-5107

Coverage

United States

Physical Dimensions

Base: 1cm high x 34 cm long x 21.5 cm across
Instrument: 48 cm high (Top of base to top of eyepiece) x 32 cm long (tip of lense to tip of eyepiece) x 21 cm across
Lenses: Large central lense diameter of 7 ½ cm, Smaller side lense diameter of 4 ½ cm 
Crate: 54 cm high x 38 cm wide x 27 cm back

Materials

Instrument: Plastic, various alloys including brass, glass, water.

Case: Wood, various alloys including brass

Maker

David White Co.
Milwaukee, WI

Inscriptions

Engraving on side of Astrolabe:
PENDULUM ASTROLABE | David White Co. | Milwaukee. Wis., U.S.A. | No 67476 | M-5107 1952 | U.S. Tech I.D. Number

Property of | 38268 Michigan | Technological | University

Paper taped to front of Astrolabe above level below main aperture:

THE OPTICS IN THIS ASTROLABE | ARE COATED TO INCREASE EFFICIENCY. | CAREFUL CLEANING WILL NOT INJURE | THE LENSE SURFACES.

History of the Object

The David White Company of Milwaukee Wisconsin were the manufacturers of transits, sextants, current meters, theodolites, levels, compasses, and other engineering equipment, according to the operator's manual of the Willis Pendulum Astrolabe, which was published in 1946 and accompanies a model of the astrolabe purchased by Michigan Tech. The Astrolabe is named after John E. Willis, who invented the device in 1942 while working with the U.S. Naval Observatory. The David White Company had the honor of creating the first prototype models beginning in 1943, completing the testing phase in 1946, according to the booklet that accompanies the Astrolabe at Tech.
The box that Tech’s astrolabe is stored in is marked with a piece of tape bearing the hand-written label, OLD PRISON SITE | JACKSON MICH, suggesting that Associate Professor H.B. Anderson of the Mathematics Department found and purchased the device second-hand in 1967 when he wrote to the company for more information. Unfortunately, a copy of this letter is not with the device, although the response letter from Edwin A Setzke, Manager of Realist Inc. Customer Services Division and a booklet titled “Supplementary Information for use with the Willis Pendulum Astrolabe” which was sent enclosed with the letter can now both be found with the Astrolabe, along with the owner’s manual which accompanied the device throughout its various ownerships.
A Michigan Tech equipment number is found on the device, and tables and charts accompanying the book are filled in, suggesting that Anderson used the astrolabe in instruction.
The David White Company would continue to make the Astrolabe until 1952, according to the letter from Edwin Setzke. An inscription on the base of the Astrolabe at Tech says that the model was produced in 1952, making it one of the last astrolabes made by the company. The David White Company became Realist Inc sometime between 1952 and 1967. Realist Inc., based out of Menomonee Falls, and continued to make surveying equipment, as well as rifle scopes, projectors, and cameras well into the late eighties. The last word located on Realist Inc. was a brief New York Times article from 1989 stating that the company purchased majority stock of a Swiss company called Ammann Laser Technik AG.

Location

School of Technology, 2nd Floor, SE corner storeroom

Bibliography

Department of the Army. "Secton VII. OBSERVATIONS WITH THE 60 DEGREE PENDULUM ASTROLABE." Topographic Surveying. Washington D.C.: Department of the Army, 1953. 112. Print.

Files

PendulumAstrolabe(SchoolTech)-1.JPG
PendulumAstrolabe(SchoolTech)-2.JPG
PendulumAstrolabe(SchoolTech)-3.JPG
PendulumAstrolabe(SchoolTech)-4.JPG
PendulumAstrolabe(SchoolTech)-5.JPG
PendulumAstrolabe(SchoolTech)-6.JPG
PendulumAstrolabe(SchoolTech)-7.JPG
PendulumAstrolabe(SchoolTech)-8.JPG
PendulumAstrolabe(SchoolTech)-9.JPG
PendulumAstrolabe(SchoolTech)-10.JPG
PendulumAstrolabe(SchoolTech)-10a.JPG
PendulumAstrolabe(SchoolTech)-11.JPG
PendulumAstrolabe(SchoolTech)-12.JPG

Citation

Johnathan Jaehnig, Joachim Wright, Ben Denys, and Paul Bahle, “Pendulum Astrolabe,” Michigan Tech Inventory of Historic Scientific Instruments, accessed September 24, 2020, https://ihsi.omeka.net/items/show/4.

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