A primary astronomy .. . 68 PRIMARY ASTRONOMY. 30 3. Upon what does the apparent Longitude of a planet depend?Upon its position in the ecliptic and the point fromwhich it is viewed. 304. What is Geocentric* Longitude ? It is the apparent longitude of a planet when viewedfrom the Earth. 305. What is Heliocentric] Longitude ? It is the longitude of an object as seen from the Sun. GEOCENTRIC AND HELIOCENTRIC [In this cut, the planet B, when viewed from the Earth at A, seems to be in the signo^ ; but when viewed from the Sun, it appears to be in JJ. Again: when at C, herapparent longit
A primary astronomy .. . 68 PRIMARY ASTRONOMY. 30 3. Upon what does the apparent Longitude of a planet depend?Upon its position in the ecliptic and the point fromwhich it is viewed. 304. What is Geocentric* Longitude ? It is the apparent longitude of a planet when viewedfrom the Earth. 305. What is Heliocentric] Longitude ? It is the longitude of an object as seen from the Sun. GEOCENTRIC AND HELIOCENTRIC [In this cut, the planet B, when viewed from the Earth at A, seems to be in the signo^ ; but when viewed from the Sun, it appears to be in JJ. Again: when at C, herapparent longitude from the Earth is in fr|; when from the Sun, she appears to be in/ . The reader will not only perceive the difference between geocentric and helio-centric longitude, but will see why the latter more than the former indicates the trueposition of the planet. It is an easy thing, however, if one is known, to deduce theother from it.] * Ge-o-cen-tric, from the Greek ge, the Earth, and kentron, center:from the Earth, as the center or point of observation. f He-li-o-cen-tric, from the Greek helios, the Sun, and kentron, cen-ter. PEIMAEY ASTEONOMY. 69 LESSON XVII. FORM AND POSITION OF THE PLANETARY ORBITS, NODES, ETC. 306. Are the orbits of the planets perfect circles ? They are not, but are all more or less AP*K°Nelliptical. 307. What is the point nearest the Sun !called ? I The Perihelion* \ (P^k 308. What is
Size: 1583px × 1577px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1850, booksubjectastronomy, bookyear18
