Visibility of Luna and Lunar Crescent

Tl|rcforc, if Fothcdnghd's criGdon is nosl s@4stul i. b.i4 cotui$dr fot
negalive obedadon rhG dcs not at dl htu thrl it ii h.tcr or noa d.p.dabl. thd
Ydlop'3 mod.l. Bolh Mah&E $d FolhdinSldt hod.k @
oa resative oh6d6tioB (whd ctlsdr is mt *n) but e lc.st sussful for pciliv.
ob*d.lion. Ihh is tre sinply b..!4 the criteri! a. sficlcr s @nFGd lo o$d
crireria. On th. oih6 h.nd Babylonib @ndition, i-v.lue criedon ed lhe Luar
Riperess law e highlt cotuistent with rhe positive obervalions but l4t coNislent wilh
the ncgativ. ob*Nations. The* dd other crit.ria (Bruin's limn dnd Yallop\ 4.valuc
onedon) arc noF conc.hed with condnions ud€r rh. visibihy o{ n w lutu oesenl i3
tossible .nd not *nh fte .onditions un<ld which ir is idp6siblc.
ln kms of ovmU coosislcncy M.!Mc6 mcthod atpcd lo bc best, HoBevcr,
Bruin'r lini! Y.llop s 4-valu. cnrcrion, Lufu RiD€n.s law and o$ r-vdG ciieion @
ba*d on ene Iheoelic.l co.sid.radons &d ihc orhcr hctlDds m only empiri@I. Thc
methodr bai.d on @y thcore cal @nside€rion ndy bc inproved with be d
unde6ta.dilg ol etual physical ed physiologicat dpccts of the probhn.
4.s DISG.USq!9N
In this chapter rh. tobten ofde 6El vkibilny ofnew t6d cEscenr is cxpto..d
on de basis of pbysical modeh d6cribiiS rhe bnSlttncs of c@$ot and that of rhc
lMligh sty. Tn * nod.ls ha€ @u6cy of 2oyo vhjch is erhjbned in de succs
Ftqiag. of Edin's lihir. Yallop,s 9-v.t@ crit€,ion .nd ou r-value cntedon eith
ov€all @Nisr.my of?9.q/.. ?9.5% &d ?5.4% (espelivelr) wilh Ihe obseryatiotu. AU
th* hodeb have tngh s@ss perolag. (90% ed plu) for posilive obFNarioB
(eheo Ih. crcse.r wa Epo.ledly sn). Wilh horc accudtc nodets of biehrles or
c6c.nr &d r*ilighl sty $s. merhods cd be ihproved funher.
Th. physical nodek co.lid€rcd in tht chaprer cd bc divid.d iflo rm clses
On€ th,r b ba.d diectly on ln. brighrn* nodets and includ6 onty fi€ algoljlhn du€
ro sch4fd Thc orh.. ct$ or nod.ts dcdec !tuibihty @ndirjoN o; lhe basn of
t6l