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Questions tagged [skyfield]

Skyfield high precision scientific astronomy library for Python and NumPy

The Skyfield project provides a modern alternative to the elderly PyEphem astronomy library for Python. Instead of requiring a custom C extension to be built or installed, Skyfield does all of its computation in pure Python and requires only the NumPy high performance numeric library in order to do its work — making Skyfield perfect for developers who can install NumPy directly, or who use scientific distributions that install NumPy automatically.

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Why do calculations provided by Skyfield not match actual data?

I wanted to compare the semimajor axis that Skyfield calculates with the one from TLE. from skyfield.elementslib import osculating_elements_of as OE from skyfield.api import EarthSatellite, load, utc ts = load.timescale() sat =…
Raksha
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Skyfield topocentric to ICRS transformation. Is there anything like SOFA / ERFA atic13?

I'm currently working on astronomy mount support tool. This need to transform coordinates between JNow and J2000. I've don this using the ERFA implementation in the SOFA library, which is also present in astropy. As I starting in looking after…
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Calculate RA DEC/AZ EL of Lagrange Points seen from a location on earth

I would like to calculate the position of the five Lagrange points in the sky (L1 - L5) as RA/DEC or AZ/EL when provided with a UTC timestamp and a Lat/Lon/Alt observer location on earth. I was looking at pyephem, pyorbital and skyfield but as far…
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ECEF to J2000 using skyfield

Say I have (ECEF) latitude, longitude and distance to Earth for an object at certain time. I need to get J2000 coordinates of it. What I'm doing is import skyfield.api planets = skyfield.api.load('de421.bsp') earth = planets['earth'] ts =…
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skyfield finding outer planets

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 =…
brian lee
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How to calculate distance to comets using Skyfields?

I'm using skyfield to compute the relative distance of planets to Earth as a function of time (as described on the skyfield home page). It works great and now I'm trying to implement Earth=>comet distance (e.g. 67P/ Tchouri). I've found at NASA JPL,…
Fabio
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Vector values in ICRF to calculate angular separation

I'm trying to get my head around the concept of the values in ICRF. I wanted to calculate the angular separation between 2 or more objects with a known R.A and Dec. Referring to this question, I need to provide the x,y,x vector value for the…
Shahrin Ahmad
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Is it "OK" to just start adding attributes to Skyfield objects?

Here, "OK" means of course AYOR (at your own risk), but otherwise there are no foreseeable problems if one avoids obvious clashes with existing attributes names. Skyfield objects - especially planets - typically have a limited number of attributes.…
uhoh
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Convert a direction (vector) to R.A. and Dec in Skyfield

Within Skyfield, if I have a vector (x, y, z) from the center of the earth, how can I back-convert it to a point on the "Celestial Sphere" (i.e. Right Ascension and Declination)? For example purposes, suppose I have a few points in the orbit of a…
uhoh
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How to add JulianDate objects or offsets in Skyfield

The JulianDate object in Skyfield is a handy way to quickly produce and hold a set of time values in Julian Days, and pass them to Skyfield's at() method to calculate astronomical positions in various coordinates. (see an example script) However, I…
uhoh
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Heliocentric Positions

Is there a way to calculate heliocentric planetary coordinates (longitude and latitude) with Brandon Rhodes' python program, Skyfield? If I only do: mercury(utc=(1980, 1, 1)).ecliptic_latlon() I get a Barycentric object, and therefore the latitude…
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Where are jplephem ephemerides api documented?

I am working on what is likely a unique use case - I want to use Skyfield to do some calculations on a hypothetical star system. I would do this by creating my own ephemeris, and using that instead of the actual one. The problem i am finding is…
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why skyfield satellite position reading calculations are different from n2yo?

I am trying to track the satellite and getting its location in form of latitude, longitude and height from TLE data. But when I try to match it with the realtime readings on n2yo website, my latitude has difference of 5 degree and longitude…
Rahul Sharma
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Calculate the crescent moon width using Skyfield

How can I calculate the topocentric crescent moon width for a given time and location? I've searched through the Skyfield documentation and can't find anything. If there is no direct api what is the formulae required to do it indirectly? The closest…
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Skyfield Moon Coordinate System Conversion

I am working on a project in which I need to calculate the angle of the sun for a position on the moon. I can achieve this with the following code (adapted from Skyfield Docs here): lunar_latitude = 55.0, lunar_longitude = 86.4, lunar_altitude =…
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