Visibility of Luna and Lunar Crescent

Wlen a ctirerion allows oprielty uaid.d visibitiry of rhc ncw crcsnr dd ihe
cFsnt is nol sn thcn it is a ncgativc.@t. Th.re c& be a.mbd of ree.s tor
negativ€ em6. D.Airc rhe f&r rhal s obsd€i may b€ .xFrioed ed r.ined
dlononer &d lmws the loerion offie cEsent rhe armosphdic €ondilions od the
Physioloey of dc obw.at cy6 @t stil lead lo non-vbibilny of ihe crent Thes
facloB ae sdlt nol wll exploEd rhus the high frequency ofrhc..gaive crc6 shos
Oil the probLm is srill nol eh.d conpl.Iety. A posniv. emr @cG when a nodel do*
allow visibihy oa cesc. sd thc visibitiry is nor claimed Snaltq rhc n!frb€r of
posirive ercB dd b.ttq is a visibility c.irerion.
The hbl€ 4.4.5 slmdises the posnile ed negative obseNarioB in 6greoe.t
or d'esrem. with diafcEnr oilcrion fmn ft€ dara sr w h.ve choen for $is M,k,
Tte labl€ is aEanScd wirh dercsing succe$ pcrce age in tems of vjsibiliry claihs
aruirenl wirh lhe $ircrion. Surprisingly lhe Babylonim cnrenon ha rhe besr succcs
percenh8e ti)ttow€d by our r-vatu. cril€rioo, Th. l.btc funher shows lh Btuin,s
cnrenon (4,1_2) and th. L@r Ripens law e.qudly suae$tuI, Thse @ followed
by $. q-valu. critcnon of yalop dd rnc ARCV,DAZ_bdcd Indid ncrhod (1,6.t3)
Tlle crn*ion duc ro Ma@dd (3.6.10) od lo$erinsnd,s crjterion aE dD lc6t
sucessful ofde mdhods shom in rhc |2bte, Ir sbould i, nor.d lhar tess succdstut a
modd is in d€$nbine pGilive sighdnS gncEr it is. Moreoler, strcrer a hodel jt should
be nore coosislenr wirh .cgaljve obs€ryatioDs (wl|en fte cGsc.hl ,s nor sn).
,
The number of iegarive obsrnadons in ag@mc urh lhc diterioo is at$
omrdkd 6 a resl of a cnr.non by sodc alrhos (Fatooni et ot, 1999). Howe!e!! ii
should be notcd $ar rhe exploration of Scha€fcr shows fior $e bneh|ness or nagnnude
contra$ is highty dcpendenr on rhe w.alher .ondir io.s. All rhe single pameter cn&ria
consdsed in the rable 4.4.5 do nor conlider wea$er ondiriotu of indilidu.l
obsw.'r'on.If ay ofd* qitcdon alom viribility in soh€ cae il ,. sl,U possibte lhal
lne setbq @ddirioN &c rcr f.vour.bk for vkibiliry &q oe crc*en is not acrualty
166