Visibility of Luna and Lunar Crescent

e{inctton .nd sky briShtn* ds€ to vanou. objocrs l6adtn€ to th€ ttmtttng
ma€l tude or the sky. H6 al$ lhe.att2od rhe hportance ot (a) tack ot hrorm.lton
about seather predrclton st iems a.d (b) necd ot tunher qtlo.6 on ot th6
physlolos/ of huhan vi3lon c.pabthbs. Thus,3tnc6$€ rheoFltcat modet teadi€lo
Lunar Rlp€nes law by modtqvat Mus ms th6 only rheoreltcat mod€ts a€ du€ ro
Bruln and Schaeter In rhl. york Schaoter'. t$hntque! .16 .pptied ro th6 ,6cent
obs.aalion.l data and a.e toond to b6 In good aet!€metrt wtrh the obsetoalonal
The exptotts or yattop (ya[op, 199a) whlch was .gatn mor€ of enoticat tn
.aruE b ba36d on the ob$da{onat dsta and p.n o, Brutn,. mod6t bur wtrh rhe
srmprrcrt ot a 5tngl6 par.meref crito.ton tor the n.w oes.enr usibtr(v, Thls
Yallop s modet c.. b€ termed as a s.mbmpt car moder. one o, rh€ m6t
srgnlllc.nt connbutons ot y6lop ts hts concept of b€st th€ of vistbfiiy, Tne
sonware Hrtatol computes borh th. q_vatues (ya op, 199a) and rhe naCrltod€
@ntrst (rhe rerm cotned In rhts work) rhal tsthe dnf.ron@ o, rhe r{agnjtud€ ot tho
llroon and th. timtflnS hagnltud6 of rhe sky ctos6 to cr€*enr. Ihe conpartson ot
lh€ tso i3 di$ussed ..d som. ot th6 extra ordtnary oDsendtbns are cdflc.flr
analy$d. rlle mosl stgniftcant part ol thts ch6pter ts the d€vetopnenr ot a new
srnge psrsmeter crttodon for th€ fl6r vistb lty o, new tuhar crsc6nt, we have
con3ld€red the acruatbnghrne$ ot the cr6c6nt rhat b pnase dep.nd€nt(instead of
aver.€. bd€ntnBs ot ihe tul Moon ctos. to horizon usod by sruh).nd rho.ctual
b ghrne$ ot lh€ iw ght 3ky close lo rhe potnt whee rn€ cesce rs prese( For
lh€ bighhe$ of bolh (the 63conr and th€ sky) the loots devoloped Schr.fer.nd
otheE hav6 been osed, thts has ,6!utted hlo new vlrtb tty and lmtring vbtb iry
cunqr lhb te6ds to a n€w s€t of basic dat. whtch In run E.onvened hro a rcw
slnge paramoter cdredo. ba*d on . retarion het e€n aRcv and width o, crescenl.
lh6 osr mod.t ts anorh€r somfempnbat modot, Our cdterion is lo{.(t to havo
bettor succe$ percentago than any orh.r crile on devetopod dq ng rh€ 2Oh
t26