Rosete-Aguilar, "Selection of glasses for achromatic doublets
with reduced secondary spectrum.
The achromatic doublet
design will be carried out by means of a parametric analysis to reject the less efficient configurations, thus leading to a set of optimal solutions that will be compared in terms of efficiency, stability flux distribution, uniformity, and so forth.
A large aperture achromatic doublet
like the instrument employed by Greenacre and Barr is remarkably ill-suited for assessing any 'delicate' colour phenomena.
Designated an official product of the International Year of Astronomy 2009, this compact 80-mm achromatic doublet
sports a 11/4-inch rack-and-pinion focuser with integrated T-thread adapter, and a mounting bar with 1/4-20 threaded holes to attach the scope to an included photo tripod.
Later research into this effect revealed a surprising result, that is, the high reduction of the chromatic aberration of a single plano-convex objective lens by placing an achromatic doublet
lens at some position along the focal length, and inside the prime focus itself.