REM Reissued 13.1.2003 to replace crashing version on site!
      REM Jupiter's Moons  RGW 1.2.2001
      REM This is very much in development so the listing is still a mess
      REM  as its come from a very different starting program originally
      REM  for the spectrum I think.
  100 a$="h"
      flag=0 :REM to get display to halt intitially
  110 REM Jupiter's Satellites.
  120 MODE7
  130 DIM x(5),t$(5),x$(30)
  140 t$="1234J":s$=""
  150 r1=PI/180
  160 m$="JanFebMarAprMayJunJulAugSepOctNovDec"
  170 REM Titles / Date input
  180 PRINT"Gallilean Satellites of Jupiter"
  190 INPUT'"Year: "yr
  200 d$=STR$(yr)
  210 REPEAT:INPUT'"Month(1-12): "mh :UNTIL mh>0 AND mh<12.1
  220 m$=MID$(m$,mh*3-2,3)
  230 PRINT'"Month= "m$
  240 d$=d$+" "+m$
  250 REPEAT:INPUT'"Day: "dy:UNTIL dy>.9 AND dy<31.1
  260 a$="h"
  270 d$=d$+" "+STR$(dy)
  280 REM Set up titles
  290 MODE8
  300 VDU23;8202;0;0;0;
  310 COLOUR2
  320 PRINTTAB(20)"Gallilean Satellites of Jupiter"
  330 COLOUR3
  340 PRINTTAB(0,3);d$
  350 COLOUR1:PRINT'"1: Io"
  360 COLOUR2:PRINT"2: Europa"
  370 COLOUR3:PRINT"3: Ganymede"
  380 COLOUR6:PRINT"4: Callisto"
  390 REM Calc days/leap yrs
  400 m=mh:y=yr
  410 IF mh>=3 THEN GOTO 430
  420 m=m+12:y=y-1
  430 f=INT(y/100)-INT(y/400)
  440 REM Calc Julian Day
  450 a=INT(365.25*(y+4712))-2415020
  460 b=INT((367*(m-1)+5)/12)
  470 hr=0
  480 REPEAT
  490   d=dy+hr/24+a+b-f-.5
  500   M=FNz(358.476+.9856003*d)
  510   N=FNz(225.328+.0830853*d)
  520   J=FNz(221.647+.9025179*d)
  530   aa=1.92*SIN(M*r1)+.02*SIN(2*M*r1)
  540   bb=5.5537*SIN(N*r1)+.167*SIN(2*N*r1)
  550   K=J+aa-bb
  560   delta=SQR(28.07-10.406*COS(K*r1))
  570   psi=ASN(SIN(K*r1)/delta)/r1
  580   u1=FNz(84.5506+203.405863*(d-delta/173)+psi-bb)
  590   u2=FNz(41.5015+101.291632*(d-delta/173)+psi-bb)
  600   u3=FNz(109.977+50.2345169*(d-delta/173)+psi-bb)
  610   u4=FNz(176.3586+21.4879802*(d-delta/173)+psi-bb)
  620   x(1)=5.906*SIN(u1*r1)
  630   x(2)=9.397*SIN(u2*r1)
  640   x(3)=14.989*SIN(u3*r1)
  650   x(4)=26.364*SIN(u4*r1)
  660   x(5)=0
  670   REM Print Jupiter and plot moons
  680   COLOUR3:VDU4:PRINTTAB(12,3);" + ";INT(hr);" hr"
        
  690   PROCdisplay:REM PROCwait(.1)
  700   REM PROCsort
  710   IF a$="d" OR a$="D" dy=dy+.01
  720   IF a$="h" OR a$="H" hr=hr+.01
  730 UNTIL FALSE
  740 END
  750 :
  760 DEF FNz(i)=i-360*INT(i/360)
  770 :
  780 DEF PROCdisplay
  790 GCOL0,2
  800 VDU24,1;350;1279;450;
  810 VDU29,640;400;
  820 VDU5
  830 CLG
  840 FOR moon=1 TO 4
  850   GCOL0,7
  860   MOVE 0,16:PRINT;"o"
  870   colour=moon:IF moon=4 THEN colour=6
  880   GCOL0,colour
  890   PLOT69,-x(moon)*20,0
  900 NEXT
      IF flag =0:PROCwait(5):flag=1
  910 ENDPROC
      DEF PROCwait(s):TIME=0:REPEAT UNTIL TIME>100*s:ENDPROC