THE HISTORICAL UNRAVELING OF THE DIAMETERS OF THE 1ST 4 ASTEROIDS

At the dawn of asteroidal astronomy (c. 1801-1850) the diameter of Cer es was uncertain to within a factor of 10. Today the value is quoted t o an accuracy of 0.6%. This paper discusses the way in which the estim ates of the diameters of the first four numbered asteroids have improv ed in accuracy. Over the last two centuries disc micrometers have give n way to photometers, and in their turn these have been replaced by fi lar micrometers, visual polarimeters, infrared photometers, speckle in terferometers and occultation techniques.