42 lines
1.2 KiB
Fortran
42 lines
1.2 KiB
Fortran
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SUBROUTINE COORD(A0,B0,AP,BP,A1,B1,A2,B2)
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! Examples:
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! 1. From ha,dec to az,el:
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! call coord(pi,pio2-lat,0.,lat,ha,dec,az,el)
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! 2. From az,el to ha,dec:
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! call coord(pi,pio2-lat,0.,lat,az,el,ha,dec)
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! 3. From ra,dec to l,b
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! call coord(4.635594495,-0.504691042,3.355395488,0.478220215,
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! ra,dec,l,b)
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! 4. From l,b to ra,dec
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! call coord(1.705981071d0,-1.050357016d0,2.146800277d0,
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! 0.478220215d0,l,b,ra,dec)
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! 5. From ra,dec to ecliptic latitude (eb) and longitude (el):
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! call coord(0.d0,0.d0,-pio2,pio2-23.443*pi/180,ra,dec,el,eb)
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! 6. From ecliptic latitude (eb) and longitude (el) to ra,dec:
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! call coord(0.d0,0.d0,-pio2,pio2-23.443*pi/180,el,eb,ra,dec)
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SB0=sin(B0)
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CB0=cos(B0)
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SBP=sin(BP)
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CBP=cos(BP)
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SB1=sin(B1)
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CB1=cos(B1)
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SB2=SBP*SB1 + CBP*CB1*cos(AP-A1)
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CB2=SQRT(1.e0-SB2**2)
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B2=atan(SB2/CB2)
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SAA=sin(AP-A1)*CB1/CB2
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CAA=(SB1-SB2*SBP)/(CB2*CBP)
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CBB=SB0/CBP
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SBB=sin(AP-A0)*CB0
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SA2=SAA*CBB-CAA*SBB
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CA2=CAA*CBB+SAA*SBB
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TA2O2=0.0 !Shut up compiler warnings. -db
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IF(CA2.LE.0.e0) TA2O2=(1.e0-CA2)/SA2
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IF(CA2.GT.0.e0) TA2O2=SA2/(1.e0+CA2)
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A2=2.e0*atan(TA2O2)
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IF(A2.LT.0.e0) A2=A2+6.2831853
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RETURN
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END SUBROUTINE COORD
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