iq6

Plate

L 1 V.

Fig.

Astronomy.

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i.

2. The mean Distances of the Planets front *are thus stated by Sir Isaac:

According to Kepler , %

$ ? ® & % >,o0§'

38806. 72400. 100000. 152350. 51965°- ^

According to Bullialdus ,

38585. 72398. 100000. 152350. 522520- 95According to the Periodical Times,

38710. 72333. 100000. 152369. 520096-

3. Before we can shew how the JPeriodics ^ #

and Distances of the Planets are found, Jt 6 ^cessary to premise the following Things, viz. ^.^5 !rtf a Planet is not in the Plane of the Ecliptic . £ £

ANLO be the Orbit of a Planet P, and let

be the Earth’s Orbit, which is in the Plane of thtic ; then will one half of the Planet’s Orbit n ^ fct'the Plane, as N L O, and the other Half iN ^ <

low it. 0 jr

4. she two Planes , therefore , sf the Planet’s

tf/~ Ecliptic will intersect one another , which r ca !letion will be a Right Line, as N O ; and thisthe Z/k.? of. the Nodes , the Nodes being the tv»

,ll £l

’' r

„„ so* jr

N and O, in which the Planet descends beloW, .0

VWgM

D*I £lt

N ‘ d ‘- ' ° ' i-'-L

cends above, the Plane of the Eclipticis called the Ascending Node , and N the

5. Let the Curve NwObc described in th e jjbQthe Ecliptic perpendicular under the Half

then is the Curve N m O said to be th e Prof", -u 1 ,7Planet’s Orbit N L O on the. Plane of the Eclf ttC, ^p iithe projected Place of the Planet P, cr its PL ceto the Ecliptic. ■ * if!\

6. The Angle L O in measures the Incliff *

Plane of the Planet’s Orbit to that of the Eclip ttC ’ Jjc 11 jis also called the Obliquity thereof. The Perp 5 6 ^ ?\f.Distance P p is the Latitude of the Planet from je, ,pof the Ecliptic ; and L m is the greatest L a ‘ P f tL O or L N he ^ Quarter of a Circle. Alf° . < c al' etance of the Planet from the Node, viz. ? O, ^f;he Argument of Latitude. ' ~rf.tr.

/•

vj juuinuae* rs.tp

«* T?> Tt. and ktojli -'!

is the Angle P S p the true Latitude fcen L° m