bwBASIC/B15B/sunshine.bas

10 REM    SUNSHINE
12 REM
14 P=3.14159265: R=P/180
16 INPUT "LATITUDE (DEGREES)";F
18 F=F*R
20 S=SIN(F): C=COS(F)
22 INPUT "START DAY IN 1986 ";J1
24 INPUT "END DAY IN 1986   ";J2
26 IF J2<J1 THEN 24
28 Z=0
30 FOR D=J1 TO J2
32 M=357.1663+0.9856*D
34 M=M*R
36 L=279.8603+0.985647*D
38 L=L+1.91533*SIN(M)
40 L=L+0.02001*SIN(2*M)
42 L=L+0.00029*SIN(3*M)
44 L=L*R
46 G=0.3978062*SIN(L)
48 K=SQR(1-G*G)
50 U=(-0.01454-S*G)/(K*C)
52 IF ABS(U)<1 THEN 58
54 IF U>1 THEN 70
56 Z=Z+1440: GOTO 70
58 F=0.9043+0.03023*COS(M)
60 F=F/(1-0.15825*SIN(L)*SIN(L))
62 A=ATN(SQR(1-U*U)/U)
64  A=A/R
66 IF U<0 THEN A=A+180
68 Z=Z+2880*A/(360.985647-F)
70 NEXT D
72 PRINT
74 PRINT "SUNSHINE = "
76 PRINT INT(Z+0.5);" MINUTES"
78 PRINT INT((Z+30)/60);" HOURS"
80 END
85 REM  ------------------------
88 REM  APPEARED IN ASTRONOMICAL
89 REM  COMPUTING, SKY & TELE-
90 REM  SCOPE, SEPTERMBER, 1984
92 REM  ------------------------