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    Fw: Astronomical Refraction: Computational Method for All Zenith Angles
    From: Marcel Tschudin
    Date: 2005 Aug 22, 18:33 +0300

    Strange things happened to the e-mail just sent. The code at the end of it
    got cut off and added into an attachment, which cannot be opened. I tried it
    now again by forwarding the copy in the sent-file to my own address and this
    worked. I send now a copy of this test and hope it works fine this time.
    
    >> Refering my last mail, where I mention that I can not reproduce the
    >> values shown in the Auer Standish paper using the polytropic atmosphere
    >> model:
    >>
    >> 1) I overlooked the part on the following page: "These values are used to
    >> compute the coefficients for only that associated region of the
    >> atmosphere. In order to ensure continuity, the temperature and the
    >> density must be extrapolated to the boundary, defined by the altitude
    >> hB."
    >>
    >> 2) When introducing what is described there, the results are even worse.
    >>
    >> It seems that there is something wrong in my stratospheric part. May I
    >> ask you, Frank, to have a look at it? May be you can see what is going
    >> wrong there.
    >>
    >> Thanks, Marcel
    >>
    >>>>>>>>>>>>>>>>>>>>>>>
    >> Function getmu (r : Real): Real;  // r = REarth + h
    >> var
    >> ...
    >> begin  // getmu
    >> // Poytropic atmospheres:
    >> Tw:=273.15+RefTemp;       // Tw=Temperature at reference point in ?K
    >> RHOw := 273.15/1013.25 * RefPress/Tw;   // RefPress = Pw
    >> Rw := (REarth+RefHeight)/REarth;        // RefHeight = hw
    >> Rrel := r/REarth;           // r relative to REarth
    >> rr := 1.0/Rrel - 1.0/Rw;
    >> // nPoly = Polytropic index = 5
    >> BETAw := g * REarth / ( Rgas * Tw * (1.0 + nPoly) );
    >> Rhb:=(REarth+hB)/REarth;
    >>
    >> if R<=Rhb then
    >> begin                                                      // Begin:  T r
    >> o p o s p h e r e
    >>
    >> RHOpoly := RHOw * Power( (1.0 + BETAw * rr), nPoly); // Power(x,y)
    >> calculates x**y
    >>
    >> end                                                        // End  :  T r
    >> o p o s p h e r e
    >>         else
    >> begin                                                      // Begin:  S t
    >> r a t o s p h e r e
    >>
    >> Tb:=Tw * ( 1.0 + BETAw*(1.0/Rhb - 1.0/Rw) );
    >> RHOw := 273.15/1013.25 * RefPress/Tb;
    >> GAMMAw := g * REarth / ( Rgas * Tb );
    >> rr := 1.0/Rrel - 1.0/Rhb;
    >> RHOpoly := RHOw * EXP( GAMMAw * rr );
    >>
    >> end;                                                       // End  :  S t
    >> r a t o s p h e r e
    >>
    >> // Nminus1 ... Refractive index of air minus 1: (n-1)=0.00029241
    >> getmu := 1.0 + Nminus1 * RHOpoly;
    >>
    >> end;  // getmu
    >>
    >>
    >
    >
    >
    
    
    

       
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