'               Davies equatorial mount
'               analytical calculation of angles etc
        pi = 3.14159
        GOTO ycalc
'-----------------------------------------------------------------------
'               This section calculates north stance if other   
'               variables given
'               comment out GOTO ycalc if you want to do this...
        zcm = 68.6             'height of center of mass above bearings
        y = 55.9               'N-S distance between supports
        ss = 95                'stance of south bearings
        epsdegrees = 34        'latitude in degrees
        eps = epsdegrees * pi / 180

yloop:  
        INPUT "zcm,y,south stance"; zcm, y, ss
'                               calculate N and S slant distances
        hs = (zcm - y * TAN(eps) / 2) * COS(eps)
        hn = (zcm + y * TAN(eps) / 2) * COS(eps)

'                               calculate north end stance 
   snsq = ss * ss * ((zcm + y * TAN(eps) / 2) / (zcm - y * TAN(eps) / 2))
   snsq = snsq - 4 * (zcm + y * TAN(eps) / 2) * y * TAN(eps) * ((COS(eps)) ^ 2)
        sn = SQR(snsq)

'                               angles of north and south triangles
        tanalphan = 2 * hn / sn
        tanalphas = 2 * hs / ss
        alphan = ATN(tanalphan)
        alphas = ATN(tanalphas)
        alphandegrees = alphan * 180 / pi
        alphasdegrees = alphas * 180 / pi

'                               print out results 
        PRINT zcm, y, ss

        PRINT hs; hn, ss; sn, alphasdegrees; alphandegrees
        PRINT "angle difference="; alphandegrees - alphasdegrees
        LPRINT zcm, y, ss

        LPRINT hs; hn, ss; sn, alphasdegrees; alphandegrees
        LPRINT "angle difference="; alphandegrees - alphasdegrees
        GOTO yloop

'-------------------------------------------------------------------------
ycalc:    
'                 This section calculates N-S separation of planes vs
'                 center-of-mass height if angles are given   
        eps = 34 * pi / 180
        alphas = 45 * pi / 180: alphan = 60 * pi / 180
        LPRINT
        LPRINT "zcm vs y-spacing for 45 and 60 degree wedges"
        LPRINT "zcm               y       s. stance     n. stance"
        FOR zcm = 20 TO 100 STEP 10
'        INPUT "zcm="; zcm
        y = (2 * zcm / TAN(eps)) * (-(SIN(alphas)) ^ 2 + (SIN(alphan)) ^ 2)
        y = y / ((SIN(alphas)) ^ 2 + (SIN(alphan)) ^ 2)
        hs = (zcm - y * TAN(eps) / 2) * COS(eps)
        hn = (zcm + y * TAN(eps) / 2) * COS(eps)
        ss = 2 * hs / TAN(alphas)
        sn = 2 * hn / TAN(alphan)
        PRINT zcm, y, ss, sn
        LPRINT zcm, y, ss, sn
        NEXT zcm
'        GOTO ycalc
        END