144 ^^' ^E Zach*s AJlronomJcal Ohfefvaiiom. 



Obfervations of Jupiter's fatellites at Marfeilles* 



ImmerCon of the Ift fatelHte at 



Imm. Ift fat. - ■» 



Imm. IVthJiat. was not total, but its I 



ever difappearing ; the iky was ferene, 



diftinftly. 



Emerfion of the Ift fatellite 



Em. lil fat. • 



Em. lid fat, - - * 



Em. Hid fat. . - ^ 



Em. lid fat. - * 



Em. Ift fat. 



Imm. Hid fat, * * 



Em. Ift fat. - - 



Em. Ift fat. 



Em. lid fat, 



Em. Hid fat. - - 



Erti. Ift fat; 



2 22 56 good 

 2 48 12 good 

 ight diminiflied fcnfibly without 

 and J-upiter had fix belts very 



H' 



IT is k'nown^ that the indirect method to calculate the orbits 

 of comets in a conic fe(^ion, by means of three obfervations 

 given, is rendered more eafy and expeditious if there is a pofli- 

 bility of drawing a graphical figure thj^it reprefents nearly th^ 

 orbit under conliideration, by means of which the calculation 

 is directed, and the requi;-ed elements of the comet's path may 

 be rigoroufly deterfnined* > To draw the orbit of a comet that 

 moves in a parabola or ellipfis^ the problem is reduced to find 

 the pofition of the axis and the perihelial diflance j this pofi- 

 tion of the axis will 'be' determined as foon as the angle is 

 known, that the axis forms with another line, whofe pofition 

 13 given ; this line may be an ordinate to a given point of the 

 curve, or a tangent, or a radius vedor, &c. The latter is to 



y be 



