I am new to using skyfield, is there any doc or help file that can show me on how to get the orbit of Sun and moon in ecliptic coordinate for a particular date and time. This is a follow up question of this question

  • 1
    $\begingroup$ I don't really see how this question is different from the one you link to. $\endgroup$
    – usernumber
    Nov 28 '19 at 10:21
  • $\begingroup$ @usernumber that was how can be done, this is for how can be done using skyfield $\endgroup$
    – Rasika
    Nov 28 '19 at 10:26

I cant help you with skyfield, but i usually use JPL Horizons Web interface. No installation required, you can also print it in a text file if you want:


Otherwise i found the documentation for skyfield: https://rhodesmill.org/skyfield/toc.html

And if nothing of that works, i made a little astropy script for you

from astropy import units as u
from astropy.coordinates import SkyCoord, EarthLocation, AltAz, get_body
from astropy.time import Time
import numpy as np

# Create 1000 Timepoints between Time 1 and Time 2 (one year later)
t = np.linspace(2451545, 2451545+365, 1000)

pointlist = []

#Loop through this times
for tn in t:
    # For every timepoint, create an astropy_time object
    astropy_time = Time(tn, format="jd")
    # Get Planet (as string, "earth", "moon", "mercury" etc. in aequatorial coordinates
    planet_aequatorial = get_body("moon", time = astropy_time)
    #Transform to Barycentric True Ecliptic (relative to the center of mass of the solar system).
    planet_ecliptic =  planet_aequatorial.transform_to("barycentrictrueecliptic")

    # Add a point to the orbit. Every point is described as (longitude [deg], latitude (ecliptic coords), distance (km))
    pointlist.append([planet_ecliptic.lon.deg, planet_ecliptic.lat.deg, planet_ecliptic.distance.km])
    # So pointslist is a 2D array. The rows are all the 1000 points of the orbit

# In every point there is 3 columns for [Long, Lat, Distance]

# You can also save the result with
pointlist = np.array(pointlist)

np.save("results.npy", pointlist)

  • $\begingroup$ thanks or the reply, it gives me a single point, however i want complete orbit, is that possible, my question may look silly, apologise $\endgroup$
    – Rasika
    Nov 29 '19 at 17:44
  • $\begingroup$ create a list of times (in julian days) with >import numpy as np >t = np.linspace(2451545, 2451545+365, 2000) then loop over the above code but create Time object with >t = Time(t1, format="jd") instead $\endgroup$ Dec 9 '19 at 22:47
  • $\begingroup$ did that help or should i do it for you? $\endgroup$ Jan 3 '20 at 13:01
  • $\begingroup$ yes, please. that will be really helpful $\endgroup$
    – Rasika
    Jan 18 '20 at 19:01
  • $\begingroup$ can you give me your e-mail or something? i cant post all the code here i think... $\endgroup$ Jan 23 '20 at 11:11

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.