j^S M DE Zach's JJlronomicni Ohfervatpons* 



large telefcopes, which magnify too much, and give too great a 

 tranfit between the penumbra and the true dark fhadow. On 

 that account feme celebrated aftronomers advife to ufe for the 

 eclipfes of the moon no greater telefcopes than of four or five 

 feet length. It was remarked at Paris, that in an eclipfe of 

 the moon, obferved through a tclefcope of DoLLOND,the focus 

 of its object lens being 30 inches, and likewife through a tcle- 

 fcope of five feet length ; the eclipfe appeared to begin 4^ 7^' 

 fooner, and to end 4^ Y' l^ter, through the fmall than 

 through the long tclelcope ; the like has been remarked by 

 feveral others, and it has been alfo obferved bv mvfelf. As to 

 my obfervations I am tolerably fatisfied with them, as they do not 

 differ materially from thofe of Feather le Fevre, though it is 

 known that in eclipfes of the moon no greater exa£l:nefs than 

 that of a minute can be obtained. The moon's fpots were 

 carefully obferved ; for it is known, that the mean of the ob- 

 fervations of the moon's fpots is fufficient to afcertaln the 

 longitude of a place to 4'^ or ^" nearly. M. de la Lande 

 comparing the oblervations of the moon*s fpots in an eclipfe, 

 made the 22d of November, 1760, in Vienna, by the Impe- 

 rial Aftronomer Abbe Hell, with thofe made at the fame 

 time in Paris by M. Messier, finds the difference of meri- 

 dians td be 56^ ^o^"* which agrees very exactly with thatt afccr- 

 tained by other means. 



Correfpondent 



