Visibility of Luna and Lunar Crescent

Flarively r€c.nr rimes, ho$v€r,lhc atiesr Hildu tdis litc pa,ch Sidn it ( D 5OO)
hints towards thc idponance of$c Vidrh oflhc luM crc$ent (Bruii, 1977) Thus an
elabootc stsreo of calcularioc involvcd in delemining the tinc of €licsr visibilitt
appeds to have developed only abund AD 500. Morcexplicirnentiohsofrhcsederaited
calcularions are loud ar vuios plaes in the dly Islmic litenle (Brui., 197?).
Ohe ol thc ealiesl Muslin Aircnomcr eho developed lnc lables fo. se lidnC
the luna!crescenl s lisibilitywas Yaqub lbn Tdiq (Ke.nedy. 1968).lt has bcen eponcd
in $e litcraluE (Atuin, 1977) that lbn Taliq had r.cogniad the imponance oflhc Width
(w) oflhe crescenr. Thh not only shows rhat ar rhd rine rhe varying dislance ot rhc
Moon had been rcaliud bul it aho mdc ir possible 10 inpov€ upon dc ncs cr*cnl
vnibilily cinerion. Bruin hd Eponed th Al-Ailuni had $e Falizario. oflhe tong ind
dillicult calcularions inlolved in lhe dercnnimlion tor the nev lun,r aesccm vnibitiry
lnd in hG Crloro.,os " reconrmcnded rhc work ofMuhanm.d lbn crbn At B,llani
l ltnlhook oJAtto"o,'t t?rstard to Lario by Nalino, l9|]3).
'lhe sihplc *nclioh for cadiesr vhibiliry oflunarcrescchr evotved sjnce lhe riftes
of B6btlonids qas passd onb rnc Muslims drcueh Hindus wirh !e,)-' tinle
inprclemenr. Molilated by the euEnic iijuhctions a.d rhe salnlgs of rn prollrr
Muhamnad (PBUH) rh. Fobtem ofearliest sighring of hnar cE*enl \s lhomnehl).
Invesriglredby rlrc earlJ Mrslih aslronomcGotsLhto l0'tccnluryAt).
OD the bash ofreatiarion of the idjponance ofwid$ various Arab asllonomcrs
conclndcd td lor celics( vjsibilil, ofcrc$.nl thc minimun equabrial $pararion offie
Sun lnd the Moon varics from t00 whcn lhe crescent is widesr up to l2i whcn llr
cNcc.l is n@$cst Such der,il.d calculariotr \.rc wor\cd oul.s earty as 9ri cenrur)
AD by Muslinr asrrononers as$ciated wirh rhc Ab&sid coun of Al,Mahun. Fronl
monesr the* {stbnoncf Al-BaIsli kncw lh,r ihc cnleria that.gc of n@, shoutd b€
moe tnan 24 hou6 (or arc sepdarion belveeo $e Sun sd lhe Mooh) isa good sldtine
poinr but i A only m appnrnarion. H. b€t,.vcd LlEr lhc dcienl6hnomc6 d,d nor
understohd the ph€nonenon conpteretr, According to Bruih, AtDatani,s compuradonal
sork is o very elabo6re sysr€m of mrhehari€t catculalions (Bruin, | 977).
t2