An Explanation of the Gnomonic Projection of the Sphere; and of Such Points of Astronomy as are Most Necessary in the Use of Astronomical Maps: Being a Description of the Construction and Use of the Larger and Smaller Maps of the Stars; as Also of the Six Maps of the Earth |
Other editions - View all
Common terms and phrases
Aldebaran angle of position appear ascension and declination astronomical Auriga Capella axis Bayer Boötis called Canis Cassiopeia catalogue centre Cephei Ceti colour comet cone constellations contains Coronæ cube Cygni degree described diameter diurnal motion double stars Draconis earth ecliptic ellipse equal equator equatorial figure fixed stars Flamsteed Geminorum globe gnomonic projection Greenwich heavens hemisphere Herschel Hipparchus horizon hour circle Hydræ hyperbola instrument latitude latter Leonis lines drawn longitude look magnitude mean solar measuring meridian Messier method micrometer Minoris minutes move nebula north polar objects Ophiuchi opposite orbit Orionis parallel pass Pegasi planisphere pole portion preceding precession proper motion Ptolemy represented revolution right ascension screw side sidereal sidereal day small circle small star solar day south polar maps spectator sphere straight line suppose surface telescope tion Ursa Majoris vernal equinox Virginis visible whole Winter Solstice wire
Popular passages
Page 27 - The circumference of every circle is supposed to' be divided into 360 equal parts, called degrees ; each degree into 60 minutes, and each minute into 60 seconds. Degrees, minutes, and seconds are designated by the characters °, ', ". Thus 23° 14' 35" is read 23 degrees, 14 minutes, and 35 seconds.
Page 92 - To imitate the motions of the planets in the above-mentioned orbits, Mercury must describe its own diameter in 41 seconds; Venus in 4 minutes 14 seconds ; the Earth in 7 minutes ; Mars in 4 minutes 48 seconds ; Jupiter in 2 hours 56 minutes; Saturn in 3 hours 13 minutes; and Uranus in 2 hours 16 minutes.
Page 92 - On it place a globe, two feet in diameter ; this will represent the Sun ; Mercury will be represented by a grain of mustard seed, on the circumference of a circle 164 feet in diameter for its orbit ; Venus a pea, on a circle of 284 feet in diameter ; the Earth also a pea, on a circle of 430 feet ; Mars a rather large pin's head, on a circle of 654 feet ; the Asteroids, grains of sand, in orbits of from 1000 to 1200 feet; Jupiter a moderate-sized orange, in a circle nearly half a mile across...
Page 92 - Mars a rather large pin's head, on a circle of 654 feet; Juno, Ceres, Vesta, and Pallas, grains of sand, in orbits of from 1000 to 1200 feet; Jupiter a moderate-sized orange, in a circle nearly half a mile across; Saturn a small orange, on a circle of four-fifths of a mile; Uranus a full-sized cherry, or small plum, upon the circumference of a circle more than a mile and a half, and Neptune a good-sized plum on a circle about two miles and a half in diameter.
Page 105 - Figs. 11—12. of large stars, into which the central cluster would be seen projected, and (owing to its greater distance) appearing, like it, to consist of stars much smaller than those in other parts of the heavens.
Page 105 - ... of large stars, into which the central cluster would be seen " projected, and (owing to its greater distance) appearing, like it, to " consist of stars much smaller than those in other parts of the heft" vens. Can it then be that we have here a real brother system, " bearing a real physical resemblance and strong analogy of structure
Page 92 - As to getting correct notions on this subject by drawing circles on paper, or still worse, from those very childish toys called orreries, it is out of the question.
Page 53 - Imagine that Jupiter, fearing to come too nigh unto her teeth, layde holde on her tayle, and thereby drewe her up into the heaven ; so that shee of herself being very weightie, and the distance from the earth to the heavens very great, there was great likelihood that her taile must stretch. Other reason know I none.