<p>The Skyfield docs show <a href="https://rhodesmill.org/skyfield/kepler-orbits.html" rel="nofollow noreferrer">a way to do this</a>.
You need Keplerian orbital elements from the <a href="https://minorplanetcenter.net/iau/MPCORB.html" rel="nofollow noreferrer">Minor Planet Center Orbit Database</a>.
Chiron is a <a href="https://en.wikipedia.org/wiki/Centaur_(small_Solar_System_body)" rel="nofollow noreferrer">Centaur</a>, so you can use the &quot;TNOs, Centaurs and SDOs&quot; list (Distant.txt) instead of the whole MPCORB.DAT.</p>
<p>This code:</p>
<pre><code>import skyfield.api as sf
import skyfield.framelib as sff
import skyfield.data.mpc as mpc
from skyfield.constants import GM_SUN_Pitjeva_2005_km3_s2 as GM_SUN

DISTANT_URL = 'https://minorplanetcenter.net/iau/MPCORB/Distant.txt'

ts = sf.load.timescale()
t = ts.utc(2023, 12, 24)
eph = sf.load('de440s.bsp')
sun = eph['sun']
earth = eph['earth']

with sf.load.open(DISTANT_URL) as f:
    mpc_df = mpc.load_mpcorb_dataframe(f)
chiron_els = mpc_df[mpc_df.designation == '(2060) Chiron'].iloc[0]
chiron = sun + mpc.mpcorb_orbit(chiron_els, ts, GM_SUN)

pos = earth.at(t).observe(chiron).apparent()
lat, lon, dist = pos.frame_latlon(sff.ecliptic_frame)
print('Chiron lon={0:.3f}'.format(lon.degrees))
</code></pre>
<p>has this output:</p>
<pre><code>Chiron lon=15.456
</code></pre>

CC BY-SA 4.0
2023-12-24T01:33:20.943Z
Thank you Mike ❤️
dimitri33
CC BY-SA 4.0
2023-12-24T01:11:02.560Z
2023-12-24T01:11:02.560Z
Mike G
<p>I am able to find the current location for <a href="https://en.wikipedia.org/wiki/2060_Chiron" rel="nofollow noreferrer">95P/Chiron</a> using swisseph with a simple code  but i am interested into trying to calculate longitude crossings  including retro etc .. but at first i only want to see if there is a way to use skyfield maybe just to determine current longitude etc...   but i can't seem to find any ephemerises that has Chiron included. I know i can use Horizon  and create my own spice, but is that the only option ? are there any spice available for chiron for the next 2-5 years ... or are any deXXX.bsp that has Chiron info uncluded</p>

CC BY-SA 4.0
2023-12-23T06:47:47.780Z
will this be suitable? [Ephemeris for 95P/Chiron](https://in-the-sky.org/ephemeris.php?ird=1&irs=1&ima=1&iob=1&objtype=3&objpl=Mercury&objtxt=95P%2FChiron&tz=0&startday=1&startmonth=12&startyear=2025&interval=4&rows=25)
ayr
CC BY-SA 4.0
2023-12-23T10:18:59.863Z
Here's a Horizons plot for this year, using a timestep of 3 days. https://i.sstatic.net/cOJGq.png
PM 2Ring
<solar-system><ephemeris>
Chiron ephimeris calculations
dimitri33
# Chiron ephimeris calculations

(Asked by: username_0 on 2023-12-23)

I am able to find the current location for [95P/Chiron](https://en.wikipedia.org/wiki/2060_Chiron) using swisseph with a simple code but i am interested into trying to calculate longitude crossings including retro etc .. but at first i only want to see if there is a way to use skyfield maybe just to determine current longitude etc... but i can't seem to find any ephemerises that has Chiron included. I know i can use Horizon and create my own spice, but is that the only option ? are there any spice available for chiron for the next 2-5 years ... or are any deXXX.bsp that has Chiron info uncluded

**Tags:** solar-system, ephemeris
> **Comments:**
> **username_1**: will this be suitable? [Ephemeris for 95P/Chiron](https://in-the-sky.org/ephemeris.php?ird=1&irs=1&ima=1&iob=1&objtype=3&objpl=Mercury&objtxt=95P%2FChiron&tz=0&startday=1&startmonth=12&startyear=2025&interval=4&rows=25)  
> **username_2**: Here's a Horizons plot for this year, using a timestep of 3 days. https://i.sstatic.net/cOJGq.png  

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## 1 answers

### Answer by username_3 on 2023-12-24. Score: 3

The Skyfield docs show a way to do this.
You need Keplerian orbital elements from the Minor Planet Center Orbit Database.
Chiron is a Centaur, so you can use the "TNOs, Centaurs and SDOs" list (Distant.txt) instead of the whole MPCORB.DAT.
This code:
import skyfield.api as sf
import skyfield.framelib as sff
import skyfield.data.mpc as mpc
from skyfield.constants import GM_SUN_Pitjeva_2005_km3_s2 as GM_SUN

DISTANT_URL = 'https://minorplanetcenter.net/iau/MPCORB/Distant.txt'

ts = sf.load.timescale()
t = ts.utc(2023, 12, 24)
eph = sf.load('de440s.bsp')
sun = eph['sun']
earth = eph['earth']

with sf.load.open(DISTANT_URL) as f:
    mpc_df = mpc.load_mpcorb_dataframe(f)
chiron_els = mpc_df[mpc_df.designation == '(2060) Chiron'].iloc[0]
chiron = sun + mpc.mpcorb_orbit(chiron_els, ts, GM_SUN)

pos = earth.at(t).observe(chiron).apparent()
lat, lon, dist = pos.frame_latlon(sff.ecliptic_frame)
print('Chiron lon={0:.3f}'.format(lon.degrees))

has this output:
Chiron lon=15.456

> **Comments:**
> **username_0**: Thank you Mike ❤️  

---

