Newsgroup: it.hobby.nautica
Titolo: Altri ALGORITMI + errata corrige


**********************************************************
Step 1  Working with the Greenwich time and date, calculate the number
of centuries before (-) or after (+) 1200 1 Jan 2000.
Year                    Month                          
1997 -94,737,600        Jan  0           Jul 15,638,400
1998 -63,201,600        Feb  2,678,400   Aug 18,316,800
1999 -31,665,600        Mar  5,097,600   Sep 20,995,200
2000    -129,600        Apr  7,776,000   Oct 23,587,200
2001  31,579,200        May 10,368,000   Nov 26,265,600
2002  63,115,200        Jun 13,046,400   Dec 28,857,600
2003  94,651,200
Number for the year     ___,___,___      year ____
Number for the month     __,___,___     month ____
Day ___ x 86,400 =        _,___,___
Hour ___ x 3,600 =           __,___
Minute ___ x 60 =             _,___
Second ___                       __
                             __,___per date da Marzo 2000 in poi
                  aggiungere 86,400
Total seconds           ___,___,___ / 3,155,760,000 = 
Centuries        __.___ ___ ___ ___ = T
Step 2  Calculate the GHA of Aries, GHAA, in revolutions.  Remove the
integer part of the number leaving the decimal part.  It can be either
positive or negative.  If it is negative, add 1 to it to make it
positive.  Multiply the revolutions by 360 to convert it to decimal
degrees and if desired to degrees and minutes.
GHAA = 0.7790573 + 36,625.0021390T + 0.0000011T^2 
       - 0.0000122sin(125.0 - 1934.1T) - 0.0000009sin(200.9 +
       72,001.7T) = 
              ____._______ rev.
                _0._______ rev (decimal part)
                 0._______ rev (if negative, decimal part + 1)
                  ___.____ °     ___ ° __._ '
Step 3  Calculate the Sun's mean anomaly.
g = 357.528 + 35,999.051T
    ____.____°
Step 4  Calculate the ecliptic longitude of the Sun.
EL = 280.466 + 36,000.771T + 1.915sin(g) + 0.020sin(2g)
     ____.____°
Step 5  Calculate the obliquity of the ecliptic.
e = 23.440 + 0.015T
    __.____°
Step 6  Check to see if cos(EL) is positive _  or negative _. 
Calculate the GHA Sun.  Add 180° to the value if the cosine of EL is
negative.  Add or subtract multiples of 360° until the answer is
between 0 and 360°
GHA Sun = GHAA - tan-1(cos(e)tan(EL)) (+ 180° if cos(EL) is negative)
          ___.____°     ___ ° __._ '
Step 7  Calculate the Declination of the Sun.  Negative values are
south; positive are north.
Dec Sun = sin-1(sin(e)sin(EL))
          ___.____°     _ __ ° __._ '
****************** ESEMPIO *******************************
Step 1  Working with the Greenwich time and date, calculate the number
of centuries before (-) or after (+) 1200 1 Jan 2000.
Year                    Month                          
1997 -94,737,600        Jan  0           Jul 15,638,400
1998 -63,201,600        Feb  2,678,400   Aug 18,316,800
1999 -31,665,600        Mar  5,097,600   Sep 20,995,200
2000    -129,600        Apr  7,776,000   Oct 23,587,200
2001  31,579,200        May 10,368,000   Nov 26,265,600
2002  63,115,200        Jun 13,046,400   Dec 28,857,600
2003  94,651,200
Number for the year     -94,737,600      year 1997
Number for the month     28,857,600     month Dec
Day ___ x 86,400 =        _,864,000
Hour ___ x 3,600 =           28,800
Minute ___ x 60 =             _,___
Second ___                       __
                             __,___per date da Marzo 2000 in poi
                  aggiungere 86,400
Total seconds           -64,987,200 / 3,155,760,000 = 
Centuries        -0.020 593 201 = T
Step 2  Calculate the GHA of Aries, GHAA, in revolutions.  Remove the
integer part of the number leaving the decimal part.  It can be either
positive or negative.  If it is negative, add 1 to it to make it
positive.  Multiply the revolutions by 360 to convert it to decimal
degrees and if desired to degrees and minutes.
GHAA = 0.7790573 + 36,625.0021390T + 0.0000011T^2 
       - 0.0000122sin(125.0 - 1934.1T) - 0.0000009sin(200.9 +
       72,001.7T) = 
              -
753.4469769
 rev.
                -0.4469769 rev (decimal part)
                 0.5530231 rev (if negative, decimal part + 1)
                  199.0883 °     199 °  05.3 '
Step 3  Calculate the Sun's mean anomaly.
g = 357.528 + 35,999.051T
    -383.8077°
Step 4  Calculate the ecliptic longitude of the Sun.
EL = 280.466 + 36,000.771T + 1.915sin(g) + 0.020sin(2g)
     _461.6929°
Step 5  Calculate the obliquity of the ecliptic.
e = 23.440 + 0.015T
    23.4397°
Step 6  Check to see if cos(EL) is positive _  or negative _. 
Calculate the GHA Sun.  Add 180° to the value if the cosine of EL is
negative.  Add or subtract multiples of 360° until the answer is
between 0 and 360°
GHA Sun = GHAA - tan-1(cos(e)tan(EL)) (+ 180° if cos(EL) is negative)
          301.8001°     301 ° 48.0 '
Step 7  Calculate the Declination of the Sun.  Negative values are
south; positive are north.
Dec Sun = sin-1(sin(e)sin(EL))
          -22.9252°     S 22 ° 55.5 '
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Grazie per aver messo a disposizione il tuo metodo. Quando mi deciderò
ad imparare ad usare il sestante (spero presto) lo studierò. Però,
che io sappia, il 2000, come tutti gli anni divisibili per 400, non è
bisestile.

Con questo messaggio spero di non aver creato guai informatici (so
usare il computer quasi come il sestante).

Buon vento.