Visibility of Luna and Lunar Crescent

casrcrn st! bc forc sunsd. l hc conlEi bc(wce n lhe briebtness o f crcsccni Nd thai o r thc
rwilislr sky dcp{nds on d number of f.clou. Thcsc incllde:
P6nio! of the c@nl which n.elf is significsntlv {fTctcd bv Lhc
Tbc $.nerine orthe tieii ftom cEee fld thc sunliShr dle to (a) thc
roial amount oaair-nass the ligbi tdvels-lhrcugh. (b) thc rotal amounr ol
aeosol pesnt in lhis air. and (c) lhc slratosphctic ozonc thoush shich
rhc lighl bas lo ftvel. Th6c *!lt ring souEes cauF th. inlcnsnv of liehr
sourccs of liehr rhal includc $c S!n. lhc M@h and o$r sourcG (like
anilicial light lbat G nol considcfd in this work 8lh'v m noi s
affc(i!c during lwilisht.
The amosph{ic ldp@tuE and the relaive hunidilv
Taling in|o considmrion all lh* alldls |he to|,al brighlncss of lh ikv is
conpded at lh€ point whcE cmcol is pae lf rhe bnsl i$s of $c atv is noE than
or equal to tbe briShine$ of the ccs. ihc cGcent En nor be s(n' Eten ii rhe
brishtness of the crcsocnr is marginallv moe $an the bflghtncss ot ihc skv it is vcrv
difilculi lo loc.c lhc (erc6t withour tny oplictl lid ln $e followinS thc q@'rilalivc
bols aR di*ussed bricfly for .ll dc$ @nnuaiions:
For alirudc w.ll lbo€ horian $e lpFcnt Fsnion
anamon.tR. thc angl. ofcfmdion (Snan l953.G@n 1985). givcnby:
ofrhc crc*e isEi*d bv
x=5s.{#]*' (4.i r)
whec P is the ahoq'hcic P6$rc. / is rh. |cnFatuc and z
lhe cEscenr. for ahiildcs closr ro rhs horizin rhe following
t47