TABLES 646-648. 

 ASTRONOMICAL DATA. 



417 



TABLE 546. Numbers and Equivalent Light of the Stars. 



The total of starlight is a sensible but very small amount. This table, taken from a paper by Chapman, shows 

 that up to the 2oth magnitude the total light emitted is equivalent to 687 ist-magnitude stars, equal to about the 

 hundredth rnrt of full moonlight. If all the remaining stars are included, following the formula, the equivalent addi- 

 tion would be only three more ist-magnitude stars. The summation leaves off at a point whfcre each additional magni- 

 tude is adding more stars than the last. But, according to the formula, between the 23d and 24th magnitudes there 

 is a turning point, after which each new magnitude adds less than before. The actual counts have been carried so 

 near this turning point that there is no reasonable doubt of its existence. Given its existence, the number of stars is 

 probably finite, a conclusion open to very little doubt. All the indications of the earlier terms must be misleading if 

 the margin between i and 2 thousand millions is not enough to cover the whole. (Census of the Sky, Sampson, Observ- 

 atory, 1915-) 



TABLE 547. - Albedos. 



The albedo, according to Bond, is defined as follows: "Let a sphere 5 be exposed to parallel light. Then its Albedo 

 is the ratio of. the whole amount reflected from S to the whole amount of light incident on it." In the following table, 

 m = the stellar magnitude at mean opposition; g = magnitude it would have at full phase and unit distance from 

 earth and sun; ff = assumed mean semi-diameter at unit distance; p = ratio of observed brightness at full phase to 



TABLE 548. Duration of Sunshine. 



For more extensive table, see Smithsonian Meteorological Tables. 



SMITHSONIAN TABLES- 



