Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Accurate RA and DEC

  1. Apr 4, 2010 #1
    Could someone do an equation check:

    r,v,w and N are computed from JPL data



    Sun's true longitude:
    lonsun = v + w

    Convert lonsun,r to ecliptic rectangular geocentric coordinates xs,ys:
    xecl = r * cos(lonsun)
    yecl = r * sin(lonsun)

    (since the Sun always is in the ecliptic plane, zs is of course zero). xs,ys is the Sun's position in a coordinate system in the plane of the ecliptic. To convert this to equatorial, rectangular, geocentric coordinates, compute:
    xequ = xecl
    yequ= yecl * cos(ecl)
    zequ = yecl * sin(ecl)

    Finally, compute the Sun's Right Ascension (RA) and Declination (Dec):
    RA = atan2( yequ, xequ )
    Dec = atan2( zequ, sqrt(xequ*xequ+yequ*yequ) )







    I have been using:

    xecl = (Cos(w) *Cos(N) -Sin(w) *Sin(N) * Cos(i)) * x(k) + (-Sin(w) *Cos(N) - Cos(w) *Sin(N) *Cos(i)) * y
    yecl = (Cos(w) * Sin(N) -Sin(w) *Sin(N) *Cos(i) * x + (Sin(w) * Sin(N) -Cos(w) * Cos(N) *Cos(i) )* y
    zecl(k) = (Sin(w) * Sin(i)) * x + (Cos(w) *Sin(i)) * y

    xeq = xecl(k)
    yeq = Cos(oe) * yecl - Sin(oe) * zecl
    zeq = Sin(oe) * yecl + Cos(oe) * zecl
    where oe is the obiliqity of the planet





    also RA=N+W+v is the equation true.

    Looking for an accurate RA and DEC derived from JPL data.
     
    Last edited: Apr 5, 2010
  2. jcsd
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted