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  Surveying Instrument Collection 


E. Esdaile & Sons Pty Ltd, Sydney



Serial Number



615 x 235 x 220 mm



This is a mirror stereoscope for the viewing of stereo photographs, including 23 x 23 cm aerial photographs. The stereoscopic viewing distance of the photo pairs is 250 mm.

Schwidewsky (1959, see figure above) explains the working principle as follows: "The mirror stereoscope permits the observation of large photographs in that the distance (a) between the axis rays is enlarged by double reflection to a multiple of the interpupillary distance (a'). The figure shows a cross-section with two reflecting prisms at (1), two larger mirrors at (2), and the two component stereophotographs that are to be examined at (3) and (4). The spectacle lenses (5) mounted above the prisms (1) permit accomodation free observation and slightly magnify the images."

When the legs are fully extended, an additional unit with two telescope magnifiers (3 x) is required to view the photos. Each telescope has a field of view of 70 mm diameter. The interpupillary distance on the telescope magnifier unit (by TOPCON, Japan) can be adjusted from 56 to 74 mm. There is a springloaded mechanism to attach the viewing telescope unit.

With folded legs (and the telescope magnifier unit removed), the photographs can be viewed (1:1?) with a field of view of 100 x 100 mm in each eyepiece. The dimensions of the stereoscope with folded legs is 425 x 110 x 112 mm. No focussing is possible with folded legs (and the telescope magnifier unit removed). The function of two screw holes and two screws (on the 90 degree prisms is not known (to the reviewer).

For more details of "plotting with a mirror stereoscope", for example, see pages 158-167 in Schwidewsky, K. (translated by J. Fosberry), 1959. An Outline of Photogrammetry, Sir Isaac Pitman & Sons Ltd, London.

History & comments



in wooden box, 457 x 132 x 148 mm


some damage to black paint and surface finish


The separate (TOPCON) telescope magnifier unit carries a marker pen inscription "2".


Catalogued in September 2013 by JMR. Photo by JMR.

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