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.