Visibility of Luna and Lunar Crescent

th. output ot ihesa €ftort! b a .omplter progr.m for .natysts ot ftst
vblblllly ol luh.r cr€scent named Httatol wrttten In C.t.ngs.ge dt$u$ed 6t the end
2.I INTRODUCTION
For rhc derernination of lhc visibilily mnditions otNew lund Cre$€hl (or the
old.st lutur cresccn0 over a tocal hori2on, lhe 6Bt rask h ro deremine rhe Unive6al
Tine (uT) and dai. ofrbe scocenhic cobjucrion of thc Moo. &d rhe sb or thc Binh
of New Mmn. In ils morion tuDnd rhe Eanh rhe Mmn tralcls doud 12 deg@s frcn
rv€sr ro c6t cvery day sd iakes ovr rhe Sun in doud every 29.5 dars on thc avcm8c.
When de Moon is vcry clo* lo ve$ ot (he Sun it aprears betore the sunrie ed vhen il
N elst oilhe Sui it appcmsjusr anq rhc sunset. The lunar crcscenr is vcly rarel) lkibtc
on rbedayofthe conjLncton. Dqjon Linn(Danjon 1932. t9l6) has b.cn i.$rpreted as
a limn on Ihe hininuo clongalion ofrhe visible lu@ cE*cnr Accordine lo rhis lihir
the ruMr ccsc€nr is nor visibb if lhc elonSadon is te$ lhd ? deSEes (Do88er &
Sch.efer 194. Schaefe! 1991, yallop 1998). Thc hdimM elonSadon ot $e Moon ar
lhe dtoe of$e Eeocentdc conjuncrion is same as the inctinarion otrhe lunar orbjt fbn
rhe plo. of ectipric (50 9). When rhe Moon lakes orr rh€ Sun ar ir ndimun
elongation $c ninimun time il lal€s b molc foo bein8 / fmm rhe $n (on the .6rem
side) ro be ?o again {on &e w6om side) is eoud th,ee quans ofa day. Th6 it is
theorcdcally possible lhrl rhe qesent is t6l sen on $e dly of conjunction or is tsr
seen on the day ofconjunction. TheoEricalty n is aho possibte rbar if$e crescenr n hsl
seno. the day ofconjuncrionad rhen rhe new cEscenr 6 seen on ln. da, iller, orthc
crekenr rs rasr srn on rbe day b€to,e rhe conjurcrion .nd !h?. rh. new c@dl n *en
on the day oflhe conjunction. In th6e cM rhe cre$e r.mDs hv$ible for.oneahalf'
day. Howevcr non€ of the$ lheoletical possibihia are rcatird in practice too
freque.dy. Mosrty rhe cEscent Enains inlisible for .two-sd.a-holt, days at least,
These condnions dcpehd on tc obse(ets t@a on.
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