Visibility of Luna and Lunar Crescent

'Ihis work is nor intcndcd lo explor lhc hisbry oa Aslonon! rulatn lo thc
canie$ sigltingoflhe new lunarcresccnt. Tbe Babylonia. and the nlcdielalcilons shall
nol bc dplocd frem a hi$orical FBpecrivc, wc shall rcstricl our explodlion onl) on
rlR codprison of $cse clTons sith $os ofthe moden ons. llowcvq $c mcdiclal
narh.nalical ide6 shall b. erploEd in morc dcoil in chaprc. :1.
I.,1 CALf,NDARS AND THE CELESTIAL CYCLES
Dogeel defines calendar 6 '! syslcm ol orgaizine ,ir4 tbr fi. pupos. of
@lonins im ow cxtend.d p€riodt (Doge( 1992). tl is a schcmc lor keping an
.ccounr ol da!i.'wceks . monrh. . 'yc!6 - ceolunes and "nillennia . Thc bsic
notion bchind I calendar isor8anizingr,la.olroairiconrinuous now rhal isindcp(ndcnr
ol any ehcn. of irs orsaniztion. Ahongst lhe divisions of timc in dayi. w.chs dc
eme aR dtccrly 4sociared snh $c celestial c_aclcs. the D,"r,at, \h. Ann@l ^d
rhc
/,rur. A @nplele daily rcvolurion of lhe s\t. de DildEl norion. is Efertsd b 4 a day.
lechnicallt an apparcnr r,/df.t,' h the inlcpal bcrseen rwo successivc rransiN oflhc
Sun ar any pllcc. Du. lo thc morion of rhc Eanh mund $e Sun rhe sky appc.m ro
rclolvc round tbe Eanh very slowly (lss rban a dcste€ pn da!) and one contterc
Evolurion of sky i. rhis way is Ffmd lo 6 o ,.ar. I {hni€lr! a t opictt y.ar k trc
time inleNal bctweh lwo successivc pseges oflh. Su rluough vcdat eqlinox. one oa
r\e porn6 ol inFMcrion ol rhc celB(dtequarorand rhe actiptic
Each calendar is dilided i.to yea6. yeas inb nonths. non$s inlo vNks ed
dals Most oflh€ know calmdm rha( mcn dcviFd bd sevcn da$ in a rvak. tn
diflaent Esions md cras 4 to lodot weks halc aho bccn considercd. ltowclcr rhc
nuobcr of days in a dond hd EDained variabl. in diltcc.i calcndars md wi$in a
paniculd calcndar. Tlr scbeme. il$ce isany. ofdift€!€nl DUmb$ofdays in a monlh of
a calendar is ba$d or rnc typ. ol cal4dar, Most of lhe knom atcndars.E clarsificd
iflo dtree major typcs. Solar Calcndm. Sriclly L@r C.tcnda6 and Luni-Solar
Calenda6. A blief description is Evi.$€d in rhe foltowinel
1l