Assmann Psychrometer. Hygrometer with a clockwork fan that drives air at a constant rate past wet bulb. This causes exaggerated depression of wet bulb, so giving more precise values of humidity when referred to appropriate tables.
Asteroids. Large number of very small planetary bodies, the mean point of whose orbits lies between Mars and Jupiter at approximate distance (2-8 astronomical units) required by Bode's Law. Orbits of about 1200 have been observed; between 200 and 300 have been named; many have been observed for short periods only. Vesta is the only one discernible by the naked eye. The largest, Ceres, has a diameter of 480 miles; the majority are very much smaller.
Astigmatiser.Lens and mechanism, in a rangefinder, that causes a point of light to appear as a line of light; which can then be used to determine distance off.