Visibility of Luna and Lunar Crescent

"='"[
(289)
Sinc. ihc acienl dd thc nedieval dnes {E ACE, thc time elapscd siie fie
birlh oI New Moon lill thc sunsi of lh. d.y in quesdon, w4 eo@lly coNidecd a
signindt p&Met€r. Howev€!, in ihe tinc of MuslinvABb $lronom€rs jl had already
b.en c.lied tal 0E ACE is nor a nD&hc al padndcr, stll thc pardet* is
inporlrnl 1o calculat€. This is bccaue oflhe fact that depending on rhe aordinats of the
Mooo dd lhc seaens at lime a very "young' cEsanl ce b. ee.. Amongsl bo$ rbe
anat€u s vcll a rhe prcfcssioBl Grronom.u $@ is aluyr a conFlilion for havinS
$e €ord lo s the "youneesr" crcsr eiihd wilh oFical aid or wilhout i1.
Amongst the early nod€ls ofnew cc*.!t vnibility asltunomeB sed $c !.larion
betren rh. rcldrive altitudc (ARCV = alriMc of rhc Mmn - ahilude of lhl Sun) dd rhe
rclrriv. uimurh rDA-/ - e'murh of Lh. Su - uimdh of de M@n' Th. rso
parmeleG arc slill consideFd inporl&l as if DAZ = 0. the crcscenl is venically abole
$e point of 3uEel dd und.r such a cncM$dce the youg.st a @ll as lhc thimesl
crc$qt cd bc ecn. Wirh lugd DAZ wles only oldtr md thc thictd ccs @ be
How lhick or lhin is lh€ cEsenl al any lime cs b€ ddemined once lhe
s.pmriotr (clonsaiion) b€twn rhc su ed $c Mmn hd bccn dchi'cd usi.g (2 8 ?)
sith €nh€r horizontal coordin.les or rh€ €quatorial aordintle! This elongation or Atc or
LiSht (ARCL) hads to lh. Phde (P fiaction of the illuninatcd lund disc facing fie
obsdr) of lb. Mftn using (2.8-E). Ho*ev.a the lhicloN or $e widlh (w) or rhe
c..rral pon ol the creot des not only dcFnd on thc phe of the M@!,
't
also
depclds on rhc Elnh'Moon disrece, rh. sMc cm be ohaitcd usins (2 8 9) Dte besr
inc of lbc crcsdt visibihy sqgg€ned by Yauop is criical fot siShting lhc crcsn1
u'dd mdgjml conditions &d ce be @mpur€d sine (2 E l) sisndne i5 crirical when
68