The optics of a mid 19th Century compound microscope; the Powell & Lealand microscope

Magnification and Modeling
Ray diagram showing the three lens systems.
The Powell & Lealand microscope consists of three lens systems: The objective system, a Field lens (Lens 2), and the eyepiece (Lens 1). The total magnification was calculated to be approximately 250x and observed to be 273x.

Chromatic Aberration
dn 550nm dn 660nm
Eyepiece lens 1 0.029 0.020
Eyepiece lens 2 0.004 0.005
Objective 0.003 0.001
Difference in focus positions between Red and Green illumination
Green light
White light
Chromatic aberration is minimal when imaged through the objective lens. Eyepiece lenses exhibit somewhat higher dispersion. However, this microscope can certainly be considered "achromatic" by 1861 standards. (How they determined this.)

Resolution and Sample Images
Determining Resolution

0.01mm micrometer scale

Demonstrates <<10µm resolving power

Sample images. Parachute fabric showing individual fibers.