Visibility of Luna and Lunar Crescent

In rhb ch.pter we stan wtth a b,t.f dtscGston on retativety Ecent G
di<ov.ryofthe Babllorlan cdrorla for tho 66t 6t vbtbltty ol new tunar crcscenl. A
sel or obsenatlonal d.ta solectld from rhe r*6nt tlteratore ts lsed to examtnerhe
ments orlhe Sabylonlan cnbrbn.Thts ts folowed by 3ome sphencat trigo.omeuc
conslderations ihat are llgnlllcant tor th€ condilloN on whtch the vlsibitiry or the
invisiblllty of th6 n€w lunar'o6cont haydepend.
On lhe basls of lhe t,igonom.tdc cofttd€htion the Lunar Ripene$ funclion
altrlhuled ro rheArabs rs.xplored and a tvodlfled Lunar Ripeness raw is suggested
and examrned in vlew ot th€ ,€.ordod oEerva{ons h rhe dara sel men oned
above. Thi3 Is dono uslng iho curient k.owtedgs, loots 6nd rechniques and the
.6uts of rhls erprorarlon ar6 present6d. a[ codputational wolk ts done Gtng the
In the end ot the ch6pter the gfrpktc.t modeL due io moden asldnomeG
olrhe early 20s century ar. retstt€d and compartson ot ihe same is done wilh the
Babyronlan and the medievat mod6ts.
BABYLONIAN CRITERIA
No lrisonobery or spheriqt rrigonomelly existed till rhe halheharical
developnenb in,\rabia in lhe 9u dd rhc lorh cenlu.y AD; the probteh w6 o.ly
descnbed i. rems ofcertain obseNable paranercs shown in rhc Fieure No Ll I in lhe
dcienr and lbe early Chrhlian e6.lfdny visibitiry $ireion was deduced musl have been
basd on the observations and nedsulemenrs ot rhes observable qumtities. The figure
snows lhe sesiern bolizon a dnc when the sun S h6 gon€ r deerees bebw norizon
(the sole deprc$ion) and rhe crcsenr at M isjusr visible. AB is rhe equaror lhat nakes
an agle q, $e geogBphical latitude oflhc ptace, wirh rhe nomat ro the horizon. SM n
rhe sepeadon b€teen lhe Sun tud $e tvl@n comhonly knoM s .@ of lishl. and
16