SS i caste 
: the chart we will 
- Moon’s 
T. Hill on the Occultator. 299 
Arr. XXIX.—The Occultator ; by THomas Hinz, Cambridge, 
Mass. 
For several years past the appendix to the American Ephe- 
meris and Nautical Almanac has contained a list of occulta- 
tions, visible in the limits of the United States, west of the 
Mississippi river, calculated by aid of an instrument invented 
me, in the summer of 1842. Having been requested, by 
one of the editors, to furnish a description of the instrument 
the American Journal, I will endeavor to give it in as few 
words as possible. 
tom observations on the moon, taken from stations on the 
surface of the earth, astronomers have, with incredible labor, 
computed the moon’s actual orbit, and predicted, several years 
madvance, her apparent path in the sky, as it would be seen 
ftom the center of the earth, were such observations possible ; 
that is, as it would be seen by an observer, flying with great 
ty over the earth, with such speed, and in such a path, 
4 to keep the moon always in his zenith, aan 
The problem in calculating an eclipse, or an occultation, is 
‘0 find from this position of the moon among the stars, as seen 
_ byan observer to whom she is in the zenith, where she will 
ss a to an observer in some other position 
e 
the moon, would mark in the sky, with one end, the moon’s 
oe seocentric place, with the other, its opposite pole. 
“tue relative position as the places, Moreover, if the moon be 
nas the center of the celestial sphere, these places and 
Would keep their right position on a smaller concentric 
Poles 
Sphere, Let us then take a sphere of about sixty feet radius, or 
Small portion of its surface, as a chart. Vertically over it, at 
hee of sixty feet we place an ideal moon, while upon 
; lace a model of the earth with a ten-inch 
The projection of the center on the chart being 
teal place (or rather its pole), the projection of the ob- 
