An introduction to astronomy: designed as a text-book for the use of students in college. By Denison Olmsted ...

ECTl,1IP'SES. 14:7
ecliptic. tInele, in the spherical triangle AT5CN, right anlgled
at Mt) by hNapi's tellcorem (Art. 132,, Aiote),
Rtadxsint CM::-sit CONxsin:MNO.
Fig. 62.
/ 9
The greatest apyarcit semi-diameter of t]he carth's slladow
where the moon crosses it, computed by,article 249, is 45' 5'"',
and the moon's geatecst apparltt let semi-dialinllte is 16' 45".5,
which togethtel ci ve 1 equal to 6W2' 37".5. T1tildng thle inclination of thle 1moonl's orbit, or the anlgle MNOC (what it generally is ill these circumllllstaces) at 5~ C7', andl we have Rad x sin
-. ad( xsin, Gs62' 3Y",0
62' 3".-. sin CON xsill 5 y.' or sill.N..........
and ON:: 1.~ 25' 409".t' This is the greatest distAancee of thle
moon firomn her node at whticlh an colipse of tlhe moon can tanko
place. By varyinlg thie value of CM, col rresponlling to variations in the distances of the sun and moon from the earth, it is
found that if N'O is less thian (9t, there ma-ust le an eclipse; but
between this and tlhe limit, the ease is (ldoubtful.
VWhel the moo's disk only conmes in cotact, with the earth's
shlladow, as inl figure 52, the pleltlolneltonl is called ailn qt/mls;'
welC11 Only a p)art of' the disk enters the slhtalow, the eclipse is
said to bepatrtiat(l, al td otal if thie whole of the (lisk enters the
shiadow. ~ Tle eclipse is called centt l whlen the moon's center
coincides with thle axis of the sllhadow, whlicl happl)ns wllen theo
m10oonI at the moment of opplosition is exactly) at, her nIode.
252. Before the moon enters the eartlh's slladow, the eart't
beginis to intercept from it portions of thle sun's light, graditally increasing until te moon reaclhes the shladow. iis pa1t.ial lighlt is called thie mnoon's./>enmtt, ibr. Its limits ar'e ascer-''the linle CM is to e regcarded as thle projeciont of the line which connects
the ccenters of the moon and s ection of the earthl's shado, as seen from the
jf \WVoodltouse's Astronomy, p. 718.