19 ASTRONOMICAL anp 
place, and that whofe longitude is fought ; and muft find the 
parallaxes the augmented femi-diameter of the moon and the 
difference of longitude between the centers of the fun and 
moon, or ftar and moon, for the obferved time of the begin- 
ning or ending of the eclipfe, or occultation, at this fecond. 
place. 
We are next to find the time of the true ecliptic conjunction 
of the moon and fun, or moon and ftar, according to obfervati- 
on: And here we are to obferve, that at the beginning of an 
eclipfe or occultation, the moon is vifibly not fo far advanced 
in longitude, as the fun or ftar, therefore, if we fubtra& the 
vifible difference of longitude from the fun’s vifible longitude,* 
or from the ftar’s true longitude,-- we fhall have the vifible - 
longitude of the moon: If to this vifible longitude, we ap- 
ply her parallax in longitude, with it’s proper fign, we fhall. 
have her true longitude according to obfervation, the fun's or 
ftar’s longitude being fuppofed to be accurately given by the 
tables. If we make ufe of the moon's parallax in longitude 
from the fun inftead of her fimple parallax, which will pre- 
venta feparate calculation for the fun's parallax in longitude, 
the vifible difference of longitude being fubtraéted from, or 
added to the fun’s true longitude will give the moon's vifi- 
ble longitude nearly ; and her parallax in longitude from the 
fan properly applied to this will give her true longitude. 
The 
* The fun’s vifible longitude is found by applying his parallax in longitude with. 
the proper fign to his true longitude. 
t As the fixed flars haye no perceptible parallax, there can be no diftin&tion in 
calculations between the vifible and true longitude, 
