skyfield finding outer planets

Question

I am trying to get the location for the outer planets, and I have I just want to make sure I have the code correct.

lon = 45.138967
lat = -93.342730

ts = load.timescale()
t = ts.now()
print(t.utc_jpl())

planets = load('de422.bsp')

body = planets['SATURN_BARYCENTER']
earth = planets['Earth']

myLocation = earth + Topos(lat, lon)
apparent = myLocation.at(t).observe(body).apparent()

alt, az, distance = apparent.altaz()
print(alt.degrees)
print(az.degrees)
print(distance)

Is using SATURN_BARYCENTER the correct way to do this?

Answer 1

I don't know skyfield calls all that well but when I want to verify the calculations I obtain using its predecessor, pyephem, I'll generally go to JPL's Horizon web site. Its pretty self explanatory how to set up the same parameters in its interface. The results you get are generally going to be slightly different but close enough to verify that you're on the right track.

The url is https://ssd.jpl.nasa.gov/horizons.cgi

Using Saturn's barycenter is perfectly fine. The result you'll get if you used the planet's center are only going to be different in arcseconds, if that. The barycenter for the Saturn system (planet + moons) is probably located inside the planet anyway since its mass is much, much greater than its moons.