# Questions tagged [skyfield]

The tag has no usage guidance.

26 questions
Filter by
Sorted by
Tagged with
1 vote
51 views

### Calculating field rotation between two times

I have the formulae to calculate the rate of field rotation at any given time, and using a python script with Skyfield I can generate a a value incrementing every 10th of a second based on the live ...
• 623
604 views

### How to calculate the true distance of the sun and the earth using skyfield?

I'm trying to calculate the true distance between the sun and the Earth using skyfield. To estimate the distance at a time instance I use the barycentric coordinates of the sun and earth using the ...
• 254
199 views

### Attempting to plot solar terminator using Python and Skyfield library

Problem I would like to plot the small circle defining the visible portion of Earth for an observer at position $P$ away from the Earth, on a 2D map. In the case of the Sun, this would be the solar ...
• 321
244 views

### Rising sign/constellation at a given time and place

I am new to astronomy, and trying to learn how to use Skyfield to calculate the rising sign/constellation (typically referred to as the Ascendant in astrology). I tried a number of approaches based on ...
• 41
143 views

### Resolving variance between Skyfield-generated sun vectors and test data when both use same ephemeris

I have two functions that get TEME and GCRS Earth-Sun position vectors using Skyfield: earth_sun_vectors.py ...
95 views

### Confusion about the position of lunar perigee

I'm using python pkg named astronomy-engine.First,I find 2 consecutive perigee times of moon. ...
• 39
192 views

### What is the mathematics needed for understanding DE440 and translating it into xyz coordinates?

I would like to write my own code to process NASA's DE440/DE441 ephemerides, but I do not know the mathematics needed to do this. I understand packages such as pyephem have implemented variations of ...
• 181
109 views

### Moon position differences on JPL Horizons, GMAT, Skyfield (using DE421)

I found a relevant difference in the positions for the Moon when calculating its Geocentric position with GMAT and Skyfield (https://rhodesmill.org/skyfield/), in both cases with JPL DE421. ...
• 21
1 vote
59 views

### Transforming radio sources in a T-RECS catalogue from one field to another

I have sources that I extracted from The Tiered Radio Extragalactic Continuum Simulation (T-RECS) catalogue for a deep field. I use these sources to generate a sky model at different fields within a ...
• 11
1 vote
147 views

### Are there such circumbinary planet configurations that two suns move towards each other by the sky?

Is it possible that suns move towards each other (not necessarily in opposite directions)? Such a configuration would cause interesting dusk and midday light cycles, in my opinion. Basically the ...
• 109
169 views

### How to plot the precession of the equinoxes using Skyfield?

I'm trying to create a map of the northern sky showing Earth's axial precession, like this wikipedia illustration by Tauʻolunga: I have figured out how to plot the stars using Skyfield but I'm ...
• 133
284 views

### Light or neutrinos graze or pass through the Sun and arrive at Earth - need an expression for Sun's gravitational effect on observation direction/time

Skyfield's Github has discussion Jupiter hiccup #815 which then links back to to Non-physical gravitational deflection corrections for Solar System bodies #734. The script and plot from #815 are shown ...
• 30.7k
1 vote
130 views

### python skyfield hipparcos sun mean longitude (L)

I calculate the ra and decl or the stars as below. Can I add the sun's mean longitude L (=M+w) to: ...
• 63
90 views

### How to get high-quality sky image for specific location & date

I'm working on an ink drawing album cover inspired by this Frank Hurley photo from the First World War, and want to put an accurate starry sky behind it in my album artwork.: The tower in the image ...
• 395
897 views

### How to calculate the Earth's axial tilt (obliquity)

How can I calculate the Earth's axial tilt in degrees. I tried Skyfield, Poliastro and PyEphem. I know it's changing -0.47"/year, and it was ...
• 155
217 views

### Make a guide map to comet comet Leonard C/2021 A1 using Skyfield

Sky and Telescope's How Bright will Comet Leonard Get? includes the skymap and projected (possible) light curve for comet Leonard C/2021 A1 that will potentially reach +4 magnitude this month. It has ...
• 30.7k
121 views

...
• 63
178 views

### Skyfield missing some rise and set dates

To compute the Andromeda Galaxy Risings and Settings I essentially use this code (in a more colplex code, but this serves the purpose): ...
1 vote
284 views

### How to compute rising / setting times for stars and deep sky objects with Skyfield?

I'm trying to compute rising and settings times for various objects with the Skyfield library. While the task is quite easy and well documented for planets (using the ...
120 views

### predicting angular seperation between planetary objects and earth satellites

I am struggling to calculate the angular separation between a satellite in earth orbit and a planetary object using the Skyfield library. It's equivalent to calculating the angular separation between ...
• 21
2k views

### Calculating the position of stars at a given point in time

Is there any particular methods that help us calculate the position of a star at a certain point in time? This question is what I am trying to achieve, but for me, I do not want to use the data ...
1 vote
335 views

### RA expressed in degrees

Using the Python package Skyfield I thought that I could get the RA expressed in degrees simply by doing ra.degrees, but I get the following message this angle is usually expressed in hours, not ...
223 views

### How to find the local azimuth of the highest point of the ecliptic

I would like to use pyephem or skyfield1 to find the degree of the local horizon (starting from South = 0°) at which is located the highest point of the ecliptic. Note that I am not trying to find the ...
215 views

### Discrepancy between my results of Great Conjunction 2020 and Wikipedia

Using python-skyfield to calculate the upcoming conjunction of Jupiter and Saturn. I'm off a few minutes with the times on Wikipedia. Wikipedia Great conjunction times (1800 to 2100) Using Right ...
486 views

### How can I calculate the right ascension of an observer on Earth's surface in the TEME frame with python.skyfield?

I would like to calculate the right ascension of a point on earth as specified above with the Skyfield Python library, and I can not figure out how to do this. I know that calculating the geocentric ...
• 43
1 vote