mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-11-10 14:23:31 -05:00
39 lines
1.2 KiB
Fortran
39 lines
1.2 KiB
Fortran
|
subroutine libration(jd,RA,Dec,xl,b)
|
||
|
|
|
||
|
|
! Compute optical libration of moon at jd: that is, the sub-observer
|
||
|
|
! point (xl,b) in selenographic coordinates. RA and Dec are
|
||
|
|
! topocentric values.
|
||
|
|
|
||
|
|
implicit real*8 (a-h,o-z)
|
||
|
|
parameter (RADS=0.0174532925199433d0)
|
||
|
|
parameter (TWOPI=6.28318530717959d0)
|
||
|
|
real*8 jd,j2000,mjd,lambda
|
||
|
|
|
||
|
|
j2000=2451545.0d0
|
||
|
|
RA2000=RA
|
||
|
|
Dec2000=Dec
|
||
|
|
year=2000.0d0 + (jd-j2000)/365.25d0
|
||
|
|
mjd=jd-2400000.d0
|
||
|
|
call sla_PRECES('FK5',year,2000.d0,RA2000,Dec2000)
|
||
|
|
call sla_EQECL(RA2000,Dec2000,mjd,lambda,beta)
|
||
|
|
day=jd - j2000
|
||
|
|
t = day / 36525.d0
|
||
|
|
xi = 1.54242 * RADS
|
||
|
|
ft = 93.2720993 + 483202.0175273 * t - .0034029 * t * t
|
||
|
|
b= ft / 360
|
||
|
|
a = 360 * (b - floor(b))
|
||
|
|
if (a.lt.0.d0) a = 360 + a;
|
||
|
|
f=a/57.2957795131d0
|
||
|
|
omega=sla_dranrm(2.182439196d0 - t*33.7570446085d0 + t*t*3.6236526d-5)
|
||
|
|
w = lambda - omega
|
||
|
|
y = sin(w) * cos(beta) * cos(xi) - sin(beta) * sin(xi)
|
||
|
|
x = cos(w) * cos(beta)
|
||
|
|
a = sla_dranrm(atan2(y, x))
|
||
|
|
xl = a - f
|
||
|
|
if(xl.lt.-0.25*TWOPI) xl=xl+TWOPI !Fix 'round the back' angles
|
||
|
|
if(xl.gt.0.25*TWOPI) xl=xl-TWOPI
|
||
|
|
b = asin(-sin(w) * cos(beta) * sin(xi) - sin(beta) * cos(xi))
|
||
|
|
|
||
|
|
return
|
||
|
|
end subroutine libration
|