10 ' Sunrise-Sunset 20 GOSUB 300 30 INPUT "Lat, Long (deg)";B5,L5 40 INPUT "Time zone (hrs)";H 50 L5=L5/360: Z0=H/24 60 GOSUB 1170: T=(J-2451545)+F 70 TT=T/36525+1: ' TT = centuries 80 ' from 1900.0 90 GOSUB 410: T=T+Z0 100 ' 110 ' Get Sun's Position 120 GOSUB 910: A(1)=A5: D(1)=D5 130 T=T+1 140 GOSUB 910: A(2)=A5: D(2)=D5 150 IF A(2)0 THEN 570 560 V0=S*SIN(D0)+C*COS(D0)*COS(H0)-Z 570 V2=S*SIN(D2)+C*COS(D2)*COS(H2)-Z 580 IF SGN(V0)=SGN(V2) THEN 800 590 V1=S*SIN(D1)+C*COS(D1)*COS(H1)-Z 600 A=2*V2-4*V1+2*V0: B=4*V1-3*V0-V2 610 D=B*B-4*A*V0: IF D<0 THEN 800 620 D=SQR(D) 630 IF V0<0 AND V2>0 THEN PRINT R\$; 640 IF V0<0 AND V2>0 THEN M8=1 650 IF V0>0 AND V2<0 THEN PRINT S\$; 660 IF V0>0 AND V2<0 THEN W8=1 670 E=(-B+D)/(2*A) 680 IF E>1 OR E<0 THEN E=(-B-D)/(2*A) 690 T3=C0+E+1/120: ' Round off 700 H3=INT(T3): M3=INT((T3-H3)*60) 710 PRINT USING "##:##";H3;M3; 720 H7=H0+E*(H2-H0) 730 N7=-COS(D1)*SIN(H7) 740 D7=C*SIN(D1)-S*COS(D1)*COS(H7) 750 AZ=ATN(N7/D7)/DR 760 IF D7<0 THEN AZ=AZ+180 770 IF AZ<0 THEN AZ=AZ+360 780 IF AZ>360 THEN AZ=AZ-360 790 PRINT USING ", azimuth ###.#";AZ 800 RETURN 810 ' 820 ' Special-message routine 830 IF M8=0 AND W8=0 THEN 870 840 IF M8=0 THEN PRINT M1\$ 850 IF W8=0 THEN PRINT M2\$ 860 GOTO 890 870 IF V2<0 THEN PRINT M3\$ 880 IF V2>0 THEN PRINT M4\$ 890 RETURN 900 ' 910 ' Fundamental arguments 920 ' (Van Flandern & 930 ' Pulkkinen, 1979) 940 L=.779072+.00273790931*T 950 G=.993126+.0027377785*T 960 L=L-INT(L): G=G-INT(G) 970 L=L*P2: G=G*P2 980 V=.39785*SIN(L) 990 V=V-.01000*SIN(L-G) 1000 V=V+.00333*SIN(L+G) 1010 V=V-.00021*TT*SIN(L) 1020 U=1-.03349*COS(G) 1030 U=U-.00014*COS(2*L) 1040 U=U+.00008*COS(L) 1050 W=-.00010-.04129*SIN(2*L) 1060 W=W+.03211*SIN(G) 1070 W=W+.00104*SIN(2*L-G) 1080 W=W-.00035*SIN(2*L+G) 1090 W=W-.00008*TT*SIN(G) 1100 ' 1110 ' Compute Sun's RA and Dec 1120 S=W/SQR(U-V*V) 1130 A5=L+ATN(S/SQR(1-S*S)) 1140 S=V/SQR(U):D5=ATN(S/SQR(1-S*S)) 1150 R5=1.00021*SQR(U) 1160 RETURN 1165 ' 1170 ' Calendar --> JD 1180 INPUT "Year, Month, Day";Y,M,D 1190 G=1: IF Y<1583 THEN G=0 1200 D1=INT(D): F=D-D1-.5 1210 J=-INT(7*(INT((M+9)/12)+Y)/4) 1220 IF G=0 THEN 1260 1230 S=SGN(M-9): A=ABS(M-9) 1240 J3=INT(Y+S*INT(A/7)) 1250 J3=-INT((INT(J3/100)+1)*3/4) 1260 J=J+INT(275*M/9)+D1+G*J3 1270 J=J+1721027+2*G+367*Y 1280 IF F>=0 THEN 1300 1290 F=F+1: J=J-1 1300 RETURN 1310 ' 1320 ' This program by Roger W. Sinnott calculates the times of sunrise 1330 ' and sunset on any date, accurate to the minute within several 1340 ' centuries of the present. It correctly describes what happens in the 1350 ' arctic and antarctic regions, where the Sun may not rise or set on 1360 ' a given date. Enter north latitudes positive, west longitudes 1370 ' negative. For the time zone, enter the number of hours west of 1380 ' Greenwich (e.g., 5 for EST, 4 for EDT). The calculation is 1390 ' discussed in Sky & Telescope for August 1994, page 84. 