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164 lines
6.3 KiB
Fortran
164 lines
6.3 KiB
Fortran
subroutine moon2(y,m,Day,UT,lon,lat,RA,Dec,topRA,topDec,LST,HA,Az,El,dist)
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implicit none
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integer y !Year
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integer m !Month
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integer Day !Day
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real*8 UT !UTC in hours
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real*8 RA,Dec !RA and Dec of moon
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! NB: Double caps are single caps in the writeup.
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real*8 NN !Longitude of ascending node
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real*8 i !Inclination to the ecliptic
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real*8 w !Argument of perigee
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real*8 a !Semi-major axis
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real*8 e !Eccentricity
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real*8 MM !Mean anomaly
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real*8 v !True anomaly
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real*8 EE !Eccentric anomaly
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real*8 ecl !Obliquity of the ecliptic
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real*8 d !Ephemeris time argument in days
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real*8 r !Distance to sun, AU
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real*8 xv,yv !x and y coords in ecliptic
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real*8 lonecl,latecl !Ecliptic long and lat of moon
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real*8 xg,yg,zg !Ecliptic rectangular coords
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real*8 Ms !Mean anomaly of sun
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real*8 ws !Argument of perihelion of sun
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real*8 Ls !Mean longitude of sun (Ns=0)
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real*8 Lm !Mean longitude of moon
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real*8 DD !Mean elongation of moon
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real*8 FF !Argument of latitude for moon
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real*8 xe,ye,ze !Equatorial geocentric coords of moon
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real*8 mpar !Parallax of moon (r_E / d)
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real*8 lat,lon !Station coordinates on earth
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real*8 gclat !Geocentric latitude
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real*8 rho !Earth radius factor
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real*8 GMST0,LST,HA
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real*8 g
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real*8 topRA,topDec !Topocentric coordinates of Moon
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real*8 Az,El
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real*8 dist
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real*8 rad,twopi,pi,pio2
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data rad/57.2957795131d0/,twopi/6.283185307d0/
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d=367*y - 7*(y+(m+9)/12)/4 + 275*m/9 + Day - 730530 + UT/24.d0
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ecl = 23.4393d0 - 3.563d-7 * d
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! Orbital elements for Moon:
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NN = 125.1228d0 - 0.0529538083d0 * d
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i = 5.1454d0
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w = mod(318.0634d0 + 0.1643573223d0 * d + 360000.d0,360.d0)
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a = 60.2666d0
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e = 0.054900d0
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MM = mod(115.3654d0 + 13.0649929509d0 * d + 360000.d0,360.d0)
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EE = MM + e*rad*sin(MM/rad) * (1.d0 + e*cos(MM/rad))
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EE = EE - (EE - e*rad*sin(EE/rad)-MM) / (1.d0 - e*cos(EE/rad))
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EE = EE - (EE - e*rad*sin(EE/rad)-MM) / (1.d0 - e*cos(EE/rad))
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xv = a * (cos(EE/rad) - e)
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yv = a * (sqrt(1.d0-e*e) * sin(EE/rad))
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v = mod(rad*atan2(yv,xv)+720.d0,360.d0)
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r = sqrt(xv*xv + yv*yv)
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! Get geocentric position in ecliptic rectangular coordinates:
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xg = r * (cos(NN/rad)*cos((v+w)/rad)-sin(NN/rad)*sin((v+w)/rad)*cos(i/rad))
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yg = r * (sin(NN/rad)*cos((v+w)/rad)+cos(NN/rad)*sin((v+w)/rad)*cos(i/rad))
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zg = r * (sin((v+w)/rad)*sin(i/rad))
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! Ecliptic longitude and latitude of moon:
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lonecl = mod(rad*atan2(yg/rad,xg/rad)+720.d0,360.d0)
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latecl = rad*atan2(zg/rad,sqrt(xg*xg + yg*yg)/rad)
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! Now include orbital perturbations:
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Ms = mod(356.0470d0 + 0.9856002585d0 * d + 3600000.d0,360.d0)
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ws = 282.9404d0 + 4.70935d-5*d
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Ls = mod(Ms + ws + 720.d0,360.d0)
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Lm = mod(MM + w + NN+720.d0,360.d0)
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DD = mod(Lm - Ls + 360.d0,360.d0)
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FF = mod(Lm - NN + 360.d0,360.d0)
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lonecl = lonecl &
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- 1.274d0 * sin((MM-2.d0*DD)/rad) &
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+ 0.658d0 * sin(2.d0*DD/rad) &
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- 0.186d0 * sin(Ms/rad) &
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- 0.059d0 * sin((2.d0*MM-2.d0*DD)/rad) &
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- 0.057d0 * sin((MM-2.d0*DD+Ms)/rad) &
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+ 0.053d0 * sin((MM+2.d0*DD)/rad) &
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+ 0.046d0 * sin((2.d0*DD-Ms)/rad) &
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+ 0.041d0 * sin((MM-Ms)/rad) &
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- 0.035d0 * sin(DD/rad) &
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- 0.031d0 * sin((MM+Ms)/rad) &
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- 0.015d0 * sin((2.d0*FF-2.d0*DD)/rad) &
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+ 0.011d0 * sin((MM-4.d0*DD)/rad)
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latecl = latecl &
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- 0.173d0 * sin((FF-2.d0*DD)/rad) &
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- 0.055d0 * sin((MM-FF-2.d0*DD)/rad) &
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- 0.046d0 * sin((MM+FF-2.d0*DD)/rad) &
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+ 0.033d0 * sin((FF+2.d0*DD)/rad) &
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+ 0.017d0 * sin((2.d0*MM+FF)/rad)
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r = 60.36298d0 &
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- 3.27746d0*cos(MM/rad) &
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- 0.57994d0*cos((MM-2.d0*DD)/rad) &
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- 0.46357d0*cos(2.d0*DD/rad) &
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- 0.08904d0*cos(2.d0*MM/rad) &
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+ 0.03865d0*cos((2.d0*MM-2.d0*DD)/rad) &
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- 0.03237d0*cos((2.d0*DD-Ms)/rad) &
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- 0.02688d0*cos((MM+2.d0*DD)/rad) &
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- 0.02358d0*cos((MM-2.d0*DD+Ms)/rad) &
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- 0.02030d0*cos((MM-Ms)/rad) &
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+ 0.01719d0*cos(DD/rad) &
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+ 0.01671d0*cos((MM+Ms)/rad)
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dist=r*6378.140d0
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! Geocentric coordinates:
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! Rectangular ecliptic coordinates of the moon:
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xg = r * cos(lonecl/rad)*cos(latecl/rad)
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yg = r * sin(lonecl/rad)*cos(latecl/rad)
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zg = r * sin(latecl/rad)
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! Rectangular equatorial coordinates of the moon:
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xe = xg
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ye = yg*cos(ecl/rad) - zg*sin(ecl/rad)
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ze = yg*sin(ecl/rad) + zg*cos(ecl/rad)
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! Right Ascension, Declination:
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RA = mod(rad*atan2(ye,xe)+360.d0,360.d0)
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Dec = rad*atan2(ze,sqrt(xe*xe + ye*ye))
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! Now convert to topocentric system:
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mpar=rad*asin(1.d0/r)
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! alt_topoc = alt_geoc - mpar*cos(alt_geoc)
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gclat = lat - 0.1924d0*sin(2.d0*lat/rad)
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rho = 0.99883d0 + 0.00167d0*cos(2.d0*lat/rad)
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GMST0 = (Ls + 180.d0)/15.d0
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LST = mod(GMST0+UT+lon/15.d0+48.d0,24.d0) !LST in hours
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HA = 15.d0*LST - RA !HA in degrees
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g = rad*atan(tan(gclat/rad)/cos(HA/rad))
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topRA = RA - mpar*rho*cos(gclat/rad)*sin(HA/rad)/cos(Dec/rad)
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topDec = Dec - mpar*rho*sin(gclat/rad)*sin((g-Dec)/rad)/sin(g/rad)
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HA = 15.d0*LST - topRA !HA in degrees
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if(HA.gt.180.d0) HA=HA-360.d0
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if(HA.lt.-180.d0) HA=HA+360.d0
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pi=0.5d0*twopi
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pio2=0.5d0*pi
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call dcoord(pi,pio2-lat/rad,0.d0,lat/rad,ha*twopi/360,topDec/rad,az,el)
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Az=az*rad
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El=El*rad
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return
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end subroutine moon2
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