L’Astra is the last known stereoscope based on a design by Lucien Bize. The viewer was introduced in 1913 by Robert Pleyau, the successor of Bize’s company. The stereoscope was available for the 45x107mm and 6x13cm format and has two achromatic lenses with eyepiece blinders. It could be purchased with an optional wooden cabinet for storing the bakelite slide trays.
At first glance, L’Astra appears to be an enlarged version of the compact Polyphote, which was introduced three years earlier. The functionalities and the mechanism show similarities. The question is therefore what the reason was to introduce L’Astra.
The answer lies in the 1912 patent, which describes a mechanism that supports autochromes. This colour process was introduced by Lumière in 1907 and for stereoscope designers it meant they had to deal with thicker glass plates. Although the number of autochromes was relatively small compared to monochrome images, it was important for manufacturers to support this novelty.
L’Astra has a button on the left that can be pulled out. In this position, after a full turn of the crank, the tray with slides is moved over a greater distance over the rail to support the thicker autochromes. A normal slide tray can contain 24 slides, an autochrome tray only 12 slides.
An extra frosted glass on the inside of the device suggests that the glass at the back can be removed to place a projection device or lamp, this explains the larger size of L’Astra.