achromat


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Related to achromat: Apochromat

achromat

[′ak·rə‚mat]
(optics)
References in periodicals archive ?
This premium refractor for lunar and planetary observing sports a 4-inch (100-mm) achromat with a focal length of 1,000 mm (f/10).
At the budget end of the market, three-element (meaning they have three lenses inside) eyepieces labeled Kellner or "MA" (modified achromat) can turn in a good performance with scopes of high focal ratio, such as Schmidt-Cassegrains and traditional refractors.
Delivering 56 percent more light-gathering power than its smaller sibling (the WIDESTAR 102), this refractor consists of a 5-inch (127-mm) coated achromat of 820-mm focal length (f/6.5).
The residual spurious color of an ordinary achromat cannot be totally eliminated, but it can be reduced to almost imperceptible levels if the focal length of the lens is sufficiently long.
(By the way, achromat means "without color," while apochromat means "without color--but, we're serious this time." If someone invents a refractor with color correction superior to that of an apochromat, we're going to have to come up with a new name.)
It is a short-focus achromat, which at first glance appears similar to other low-cost, short-tube refractors.
In spite of several problems inherent in its design (especially chromatic aberration), a wellmade achromat is capable of producing superb views that are rich in detail with little false color.
The Vixen 114-ED's color performance was very good, and it is far better than any f/5 to f/8 achromat, but still not the equal of apos such as Vixen's own VX102-FL f/9 fluorite refractor.
The most common type of achromat lens, according to the company, is a doublet, a compound lens consisting of two elements cemented together.
Los objetivos fueron: Plan-Neofluar 10 X A.N 0,3; Plan Achromat 32X A.N 0,4 y Plan-Apochromat 100X A.N 1,4 (para inmersion en aceite).
Other features include 8x magnification, a two-element achromat in the objective, Zeiss's scratch-resistant T* lens coating and an automatic brightness control that self-adjusts the red LED.