Description

A very rare example of Von Helmholtz’s Phakascope. According to Hirschberg (1886: A159):”…around 1870 [Von Helmholtz] wanted to demonstrate his theory of accommodation which he had already proven with his opthalmometer. He doubled the Purkinje catoptric images by using two prisms on the left side of the box.The observer was supposed to observe the movement of these doubled images from the right side. Holland proved 100 years later that Helmholtz had committed a severe error when constructing this instrument.” Maker is H. Sittel working in Heidelberg. Shipping costs will vary with your location and requirements.