October 13, 1776 Norwich, England March 1, 1862 Kent Peter Barlow, (born October 13, 1776, Norwich, Norfolk, England died March 1 , 1862 Kent), optician and mathematician who invented two varieties of achromatic (non-colour-distorting) telescope lenses known as Barlow lenses.
The two major objectives have been to focus properly all the colours of the image at the film plane (i.e., to make the lens achromatic) and to focus portions of a beam coming from different portions of the lens, the centre or the edges, at the same point on the film (i.e., anastigmatic).
If the line passes through the achromatic point, the colours represented by its endpoints, when additively combined in the appropriate amounts, must form white; therefore, all lines passing through the achromatic point terminate on the closed curve in saturated complementary colours.
Barlow constructed (1827 32) his first achromatic telescope lens by enclosing liquid carbon disulfide between two pieces of glass.
In 1868 he invented an apochromatic system of lenses, which had even better colour correction than achromatic lenses, and in 1873 he published a comprehensive analysis of lens theory.
Such a combination is said to be achromatic.
The concept of an achromatic (non-colour-distorting) microscope objective was finally introduced in 1791 by Dutch optician Francois Beeldsnijder, and the English scientist Joseph Jackson Lister in 1830 published a work describing a theoretical approach to the complete design of microscope objectives.
J.J. Lister, a wine merchant and amateur physicist and microscopist, was elected a fellow of the Royal Society for his discovery that led to the modern achromatic (non-colour-distorting) microscope.
The achromatic point is the central point at x = 1/3, y = 1/3, where visually perceived white is located (as well as the pure grays and black, which vary only in the magnitude of the luminance Y).
The use of the microscope in discovering minute, previously unknown features was pursued on a more systematic basis in the 18th century, but progress tended to be slow until technical improvements in the compound microscope itself, beginning in the 1830s with the gradual development of achromatic lenses, greatly increased that instrument's resolving power.
5. EVOSTAR-102 (EQ3-2) Refractor £339, telescopesandbinoculars.co.uk This uses a multi-element, air-spaced, achromatic refractor – which roughly translates to crisp, high-contrast images in the viewfinder.
