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Compound achromatic microscope

Year/Period

1860-1880

Maker

UNKNOWN

Country

United Kingdom

Signature

Unsigned

Category

Microscopes

Optical 1

Compound

Optical 2

Achromatic

Size of the box (h x w x d)

26.5 × 16.9 × 14.8 cm

Size of the microscope (h x w x d)

34 × 12.5 × 13 cm

Inventory number

SM 4

Description

The microscope goes with its original box with drawer, lock and key.
The microscope can be inclined between trunnions on its inverted Y-shaped foot. Below the table a revolving stop and an adjustable mirror mounted in a swinging bracket.
Coarse adjustment works on the body tube while fine adjustment works in the usual way on the nosepiece by means of a lever and a micrometer screw. The objectives use the modern RMS thread, which dates this microscope like SM 3 after circa 1860.
There is a Huygenian eyepiece of 23.3 mm diameter, the standard value for continental microscopes. Its focal length is 51.3 mm, the magnification is 4.87×.
There are two objective lenses, one of ‘1 1/2’, the other is made up of two combinations, ‘1/2’ and ‘1/4’. The ‘1/2’ combination is loose in its mount, we improved this a bit but the contrast remained bad.

The following values were measured at the microscope’s own tube, using a Bleeker eyepiece type H5, magnifying 5×:

Objective lens 1 1/2 1/2 1/4
Focal length (mm) 24 8.76 5.85
Magnification 34.4 111.5 167.3
Numerical aperture 0.086 0.30 0.46
Resolving power (µm) 5 2 1.6
Star test coma coma coma