Astra

At first glance, L’Astra appears to be an enlarged version of Le Polyphote of the same manufacturer. L’Astra incorporates features that require a larger construction. Its mechanism is based on Bize’s final patent from 1912.

L'Astra in La Nature, 6 December 1913:

…The new design, which distinguishes it from similar devices and makes it foolproof, consists in the elimination of the carriage generally used to place the slide trays… 
This ensures the operation of the finger which lifts the slides and prevents them from passing in front of or behind the slide, as sometimes happens with other systems. A special feature, operated by means of a button placed on the side of the device, allows the finger to be adjusted depending on whether there are single slides or double slides, which are generally autochromes. The slides always remain engaged in the grooves of the tray, even when they are in position to be in front of the eyepieces. In this way we are always assured that they will fall exactly into their normal position.

Operation:
The upper section of the housing can be opened. A slide tray with an open base and grooves below is inserted into the viewer and placed on the base plate, in which a gear is mounted. One of the grooves of the tray engages with the gear. The housing is then closed. By turning the lever on the right-hand side clockwise, the rearmost glass stereoview is lifted from the tray by two metal fingers that rise through the base plate from the bottom of the viewer. The glass slide is now positioned in front of the lenses. Continued rotation returns the glass slide back to the tray. At the same time, the gear in the base plate shifts the tray, allowing the next slide to be selected.

A rotary knob on the right-hand side enables the tray to be moved quickly back and forth in order to select a specific slide. On the left-hand side, a circular drum displays the number of the selected slide.

Models:
Some Astra models support the viewing of autochromes. Autochrome slides are thicker than standard glass stereoviews and therefore require mechanical adjustment. Astra models designed for autochromes are equipped with a button on the left side that can be pulled out. In this position, and after a full rotation of the crank, the slide tray advances over a greater distance to accommodate the thicker slides. A standard slide tray holds 24 slides, whereas an autochrome tray holds 12.

Specifications:

Patents:

Number: 463687
Stéréoscope classeur
Filing: 23-12-1912, Publication: 02-03-1914, Applicant(s): Lucien Bize. via: data.inpi.fr