Visibility of Luna and Lunar Crescent

Tlre modcl for rhe calculation of cc*ot lenglh may be u$d d rh. .dli6t
visibiliry ctuerion 6uch in the smc say 6 Yallop\ cilcdon cm b. usd, Hos.ver, our
€nphasis *6 nor b dcv€lop d allcm e cdr€.ion for $c s€. This *ork ws i .nded
for a b€rter und.htdding ofthe grcme$y of the lunar cEscent md lo delelop a ne$od
for cllcuhting iis l€nsrh.
The scond md indi@t tesi of the 6odel is its conparison qitb the rcsuhs of
Ddjon ncnliored in Fal@hi el- al. Ifthe niiimlm visiblc eidlh ,/, for vdious ARCV
according lo Yallop's critcrioh is r.placed by rhe nininum ever visible cenralwid$ of
0.18 aa ninuks tlEt is equivalor b igoring $e atmospheric allst for lower ARCV
|hen the Eladon b.tsen cEscdr lcngrh and .lon9rioo bccon€s snoolh as pE*nrcd by
Schaefer (Schaeftr. l99l). The smc is shoM ii Fis. 5.1.8. The chart in figwc 5.1.8 aho
sho\s lhat limiling value ofelo.gation lor po$ible lisibilily oflh€ cEscsr is areund 8
d.grees. As our compurlrions do considerthe an'cctofparallaxrhis limil is equivatenr lo
te ? degrce linil very popultrly rlown $ DanjoD\ linit.
On thc b6is of $e calcuhred lenghs of {escenr and ns elonearior using ou
hodel the Ddjon deficicncy arcs aE calculrted igno.ing the af&ch ol ARCV by
aomula giv€n by Danjon and thal given by McNally (shown in Fig. 5.1.9 and s.t.lo
Bpedi!€ly) These resuhs ae in clos agreencnr wilh fte Fig I in Flroohi el al (lbar is a
^rrcduoion of Danjon\ lis 2)- 189