Visibility of Luna and Lunar Crescent

4J
SCHAEFFER'S LIMITING MAGNITUDE MODEI,
Ilruin (197?) ued only avfrgc brislhcrs ofsk, duinsrviliehl and rh' vanarion
of brishtrcs oinE full Moon ro obEin appNximlc cohlrsl lb! (csccnls of$rtuus
sidths ro develop hh crcsccnl lisibility cuncs dhcussed a6o!c ftc t'srltins nodel
fornalized in lms of , rclation berwen cRsenl width md thc Elalilc tltiludc ol
€{*dr ar "tal rime dcduccd by Yatlop (1998) pro!.d 1o b€ hiShlv succcssful'
lihough, the basic data cxtacled by Yallop frcm Druin s visibililv cuBcs- was
rcplaced bt rhc basic das due to Scboch (1930) (lhe Indiah nclhod) lo aFivc ar his q_
value coodidons (di$nsed abovc) for rh€ nN ces€ vhibilil! n h6 bccn secn rhlr
rcsulls iom Bruin s d,tt .re mrlgi.ally bctter dan thc lndian mcthod
'or
lhc ddo scl
Schacllcr (1988a. 1988b) oh lhc o$er hand has uscd $c phvsics of \isihilirv'
cxr.nsivclt ih rcsulrcd inro a lool (6at S€hacrdconvencd inlo a compubr Dmgmm) to
ddmine $c briebhcss ol sky at anv poi ol tinc dd for di{Icrcnl aftosphenc
rcmp€*tutes aDd rclarile humidil!. Ih rhis {ork Scbaeficls progrm h ep$duccd a'd
frade pad of the lundr crc$eni visibililt software dcvclopcd. Ililalo! ro clal@re
lisibilily cohdnions. Tlis pan of the sftld is rsi b conpurc thc sk! briSbhcss (or
linni.B magnirude) al points clos to $e cre$eht md the aPPatunt nagniiudc or lh'
lunar crcscenr ro sludy $c laryins conmsr dunng twilighr for vanous tcnpcrat!rcs and
olativc fiunidny. If rhe appaFnl brighmes of the crc$e.l h morc ddi tlE bighhcs of
lhc xrilishi sty lhc cre$e should b. visible o$cNne nor Schacflcr (1988a) himsell'
hasap!li.d a sinilar rcchnique lo @lyscthc visibililvor invhibilnv data avnilablc in his
riFc. -l he @hnique is ,Pplied to $e d a*lof rh. chap161dd the rcsulB obbiocd arc
pnqntcd in rabt No 4l l Bcforc a discussion 6n rhcs' Esuhs Schrcli'is
nldhodology t-or compulins sky briShhess undc! difeEnl ahosphcnc condithns 's
Aner rhc conjunclion thc ne* lumrcrescen{cd bc seen in rh. scslcm skv ck'sto
tne non&n md lhe Poi oa $@r Simildly the last crc$enr cm bc secn i. lbc