from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. relating to the magnitude of a star as measured by the size of its image on an isochromatic photographic emulsion
from the GNU version of the Collaborative International Dictionary of English
- adj. Of certain achromatic lenses, having the same focus for the actinic and for the brightest of the visual rays.
from The Century Dictionary and Cyclopedia
- Having the same focal length for the ultra-violet and for the visible rays of the spectrum: said specifically of an objective the color-correction of which is such that when focused by the eye it is likewise in focus for the photographic plate.
Sorry, no etymologies found.