8 votes
Accepted

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

Edit: Getting the exact value winds up being simple, but it was only later in the day that the answer occurred to me. All we need to do is ask for the altitude and azimuth of the Ecliptic’s south pole!...
4 votes
Accepted

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

The model used by the IAU has (in arcseconds) the obliquity, $\epsilon_A$ as $$ \epsilon_A = \epsilon_0 − 46''.84024 t − 0''.00059 t^2 + 0''.001813 t^3$$ Where $t$ is measured in Julian centuries of ...
  • 93.9k
3 votes
Accepted

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

An Earth-centered observer looking at that point on Earth’s surface would also be looking toward the point that is the zenith for that location on Earth. Thus, you just need to find the local sidereal ...
  • 4,754
3 votes
Accepted

Skyfield missing some rise and set dates

The rising-setting search routine is currently optimized for objects near the celestial equator, like the Sun, Moon, and planets, that spent about half the day in the sky. This assumption lets it ...
3 votes

Calculating the position of stars at a given point in time

The projected separation of Mizar and Alcor is 12 arcminutes. If they are both at a distance of 25 pc (suggested by the Hipparcos satellite), then this equates to a physical separation of at least 18,...
  • 120k
2 votes

Calculating the position of stars at a given point in time

The answer probably depends on what you want, what is 'long time' for you. Astropy offers a method to handle coordinates and proper motion: https://docs.astropy.org/en/stable/coordinates/...
  • 12.8k
2 votes

RA expressed in degrees

The text is trying to suggest that you do ra._degrees. How could the message be phrased better to make clear that the suggestion is to change the attribute name you ...
1 vote

python skyfield hipparcos sun mean longitude (L)

Thank you so much. Your comments made me look further, I found my answer in the code below. # # It was the mean_longitude (L) of of the sun I was after. ...
  • 33
1 vote
Accepted

why are my Sha and Declination calculations not the same as the answers from the Nautical Almanac?

Astronomical positions always come with a date on which they are accurate, the epoch. If you compare data with a different reference frame (like from different catalogues), you have to compensate for ...
  • 12.8k
1 vote

predicting angular seperation between planetary objects and earth satellites

I think the best way to answer your question is to "ask Skyfield" to check it for you! See .separation_from() added back in 2016. Sticking with Skyfield's methods ensures that issues like ...
  • 30.7k
1 vote

Discrepancy between my results of Great Conjunction 2020 and Wikipedia

There are no bugs in your codes. But you can make it more accurate with the following corrections (additions): Using new ephemeris series (de430 or de440) most recent one is de440. Use True equinox ...
1 vote

Can I calculate the apparent position of comet NEOWISE C/2020 F3 from a topographic position with Skyfield?

The Skyfield docs don't show a way to import orbital elements directly, but it can read any BSP format ephemeris you have. If you request a HORIZONS-generated binary SPK file for the comet, that might ...
  • 16.8k

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