Visibility of Luna and Lunar Crescent

s.lld width eould nor b. visibl.. Applying ou mod.l on lhe rc@ded vbibihv rnd
iNisibiliiy dala lvaitablc fic ldgth ofcEsenl in 4ch ce is calculaiql Thc calcnlaled
lenSrhs of c$en1 @ al$ omParcd wih thc obseded leheths dd wi$ thc lengds
catculsred uing fodlls (t.1.3) de b McNally md (s.1.4 & 5 1 5) due b Slltan. ln
cs ofusing McNally's fomuh AA is @nsidded liom lhe cilerioD used in lhis work
&d for Sul|!n's fomula the ninimM width or Bl&kwll disc (,) it 66ideEd b be in
the d.ge 0.14 alc minul€ io 0.16 arc Finut€ and dep€nds on the dislane b.tqeen Eanh
&d th. Mmn obtained using simpl. lined inieQolalion
Irvi€wofQueshi & Khan (QuEshi & Khan,2007) tlre bLishrn€s ofcfsenr ar
displacement v frcn a cusp is gvei bY
8.. = tF...Cdv tr -cos t)+
(5.r.6)
sh* t G th€ radius of Moon, F. is fie mdimun nux of sunlight
olVoon.l islhc 'ePar-rion
berqecn lhe Sunand 'te
Moon in our
the lutu suface dd X B th€ disldc. of the M@n ftom the Eanh'
lhe cescenl at angular sepaElion V fom lhe cusP is eivcn bv
lV,r, =rcosWll CosE) = tl ccatv
(5.!.7)
whc t/. is lh. width of fie cdnr i! lne diddle ln bolh the* €quttioc !' vari6 lmh
oo ro 9Oo alo.g fie lenerh of rhe cFscent frcn centE ro a cusp respeclverv
For rhc develop'nen( ofanv nodel thai dcsibes $e ni'inun Po$ibl' sidlh rhtt
cd bc visiblc lttrough naked eve one requi.es 10 s'ek guidance fron $e aclual
obedalioN. ln $e history of *idtjficatlv rcponcd obeNation of thc srv voug
cr.sent Moon, lh€ ecord is that due lo Pi.rce od February 25' 1990 (eporled bv
s.h!.fd ad Yatlop) Thc cl€*nt he claift |o have sn wirh narcd ev' B jusl 14 E
houB and ils widrh wa3 O 18 dc minut€ Amonesl
'll rfie '*oded ob*flalios lh'
t11