Year/Period |
1870-1890 |
Maker |
CROUCH |
Country |
United Kingdom |
Signature |
Henry Crouch / London / 4804 |
Category |
Microscopes |
Optical 1 |
Compound |
Optical 2 |
Achromatic |
Size of the box (h x w x d) |
30 × 17.7 × 15.1 cm |
Size of the microscope (h x w x d) |
28.5 × 14 × 14 cm |
Inventory number |
SM 5 |
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.
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