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Compound achromatic microscope

Maker

CROUCH

Country

United Kingdom

Signature

Henry Crouch / London / 4804

Category

Microscopes

Optical 1

Compound

Optical 2

Achromatic

Size of the box (h x b x d)

30 × 17.7 × 15.1 cm

Size of the microscope (h x b x d)

28.5 × 14 × 14 cm

Inventory number

SM 5

Description

With the microscope goes its original mahogany box with a leather carrying grip and a lock and key.
Coarse focussing is by means of rack and pinion, however the body tube can also slide up and down in a slit sleeve. Fine focussing is by means of a micrometer screw acting on the limb. Below the stage a curved revolving stop and a mirror in a swinging bracket. The body tube is adjustable, its minimum length is 160 mm.
The Huygenian eyepiece has a focal length of 35.1 mm, its magnification is 7.1×.
There are two objective lenses, ‘2/3’ and ‘1/6’, both use the standard RMS thread. They were measured with the Bleeker microscope, using a 175 body tube and a Huygenian eyepiece magnifying 5×.

Objective lens 2/3 1/6
Focal length (mm) 13.74 3.86
Magnification 59.04 246
Numerical aperture 0.18 0.71
Resolving power (µm) 1.6 < 0.8

Objective ‘2/3’ shows a bit of coma, the contrast of the image is good, spherically it is well corrected.
Objective ‘1/6’ is well corrected in the centre, in the outer zone coma increases. Its contrast is less good.

See also SM 7.