<p>I'm trying to build an accurate model of the Solar System in Blender (a free 3D software). I relied on NASA-provided values so far for the orbits of Mercury, Venus, and Earth, but the question that bothers me is the orientation of the axis of rotation of these objects relative to the ecliptic. For Earth it's easy - Earth at the vernal equinox lies on the primary direction in the ecliptic coordinate system, which is the system I'm using for my model, and it's the point at which the celestial equator and the ecliptic plane intersect; therefore, we can easily orient the axis of Earth's rotation at 23.45 degrees as seen in the picture below.</p>
<p><a href="https://i.sstatic.net/wUl9ToY8.webp" rel="nofollow noreferrer"><img src="https://i.sstatic.net/wUl9ToY8.webp" alt="if represented by three perpendicular axis, at the vernal equinox one would point directly at the sun, the second one would be oriented along the path of the planet in orbit, and the third could be rotated to fit the axial tilt of the object" /></a></p>
<p>Source: <a href="https://www.weather.gov/cle/seasons" rel="nofollow noreferrer">https://www.weather.gov/cle/seasons</a></p>
<p>That raises a problem - although planetary axial tilt is well known for each Solar System object so far I cannot seem to find coordinates of equinoxes for other planets, that is, places at which celestial equators of the planets intersect planes of their orbits. That makes orienting their poles of rotation really hard within the software.
I've seen the data on the Wikipedia page - J2000 coordinates of objects' pole coordinates in the equatorial system, but I still wonder whether there's an easier way to do this; All I need would be the longitude of equinoxes/solstices (assuming the inclination of the orbit is 0, similar to the longitude of periapsis) of various planets and rotating the axis accordingly.</p>
<p><a href="https://i.sstatic.net/BHWVPkZz.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/BHWVPkZz.png" alt="Earth at vernal equinox in my model" /></a></p>

CC BY-SA 4.0
2024-08-04T03:04:06.557Z
You may be interested in the answer to this question: https://physics.stackexchange.com/questions/661180/where-i-can-find-obliquity-direction especially the linked PDF: https://aa.usno.navy.mil/downloads/reports/Archinaletal2011a.pdf
Sub 6 Resources
CC BY-SA 4.0
2024-08-04T03:06:16.553Z
The comments on this question, though, seem most helpful. Especially the last one which gives you an API call you can make to get the vector from a planet's center to its north pole: https://astronomy.stackexchange.com/questions/58099/how-to-get-the-direction-of-the-rotation-axis-of-a-celestial-body-using-jpl-hori
Sub 6 Resources
CC BY-SA 4.0
2024-08-04T19:23:53.787Z
Guess I got the image from https://www.weather.gov/cle/seasons
Alex MB
CC BY-SA 4.0
2024-08-04T19:29:17.213Z
@Sub6Resources Thank you for the pdf file, it appears to be a place from where the Wikipedia values were taken. Now I'm thinking of converting my model to an equatorial system, orienting the poles, and converting back to ecliptical
Alex MB
CC BY-SA 4.0
2024-08-04T22:07:39.900Z
@AlexMB thanks! I've moved the credit back into the post itself - comments are considered temporary; moderators (or the owner) can delete them at any time, so we try to keep the important bits in the post itself. Also, I noticed "if represented by three perpendicular axis, at the vernal equinox one would point directly at the sun, the second one would be oriented along the path of the planet in orbit, and the third could be rotated to fit the axial tilt of the object" inside the image link, but it doesn't appear to the readers - did you intend for that to be a visible part of the post?
uhoh
CC BY-SA 4.0
2024-08-05T09:46:55.040Z
@uhoh Thank you. I guess I expected that piece to be visible but the point is conveyed regardless so it's fine
Alex MB
<solar-system><equinox><axial-tilt>
Coordinates of equinoxes/solstices for Solar System planets
Alex MB
# Coordinates of equinoxes/solstices for Solar System planets

(Asked by: username_0 on 2024-08-03)

I'm trying to build an accurate model of the Solar System in Blender (a free 3D software). I relied on NASA-provided values so far for the orbits of Mercury, Venus, and Earth, but the question that bothers me is the orientation of the axis of rotation of these objects relative to the ecliptic. For Earth it's easy - Earth at the vernal equinox lies on the primary direction in the ecliptic coordinate system, which is the system I'm using for my model, and it's the point at which the celestial equator and the ecliptic plane intersect; therefore, we can easily orient the axis of Earth's rotation at 23.45 degrees as seen in the picture below.

[![if represented by three perpendicular axis, at the vernal equinox one would point directly at the sun, the second one would be oriented along the path of the planet in orbit, and the third could be rotated to fit the axial tilt of the object](https://i.sstatic.net/wUl9ToY8.webp)](https://i.sstatic.net/wUl9ToY8.webp)

Source: <https://www.weather.gov/cle/seasons>

That raises a problem - although planetary axial tilt is well known for each Solar System object so far I cannot seem to find coordinates of equinoxes for other planets, that is, places at which celestial equators of the planets intersect planes of their orbits. That makes orienting their poles of rotation really hard within the software.
I've seen the data on the Wikipedia page - J2000 coordinates of objects' pole coordinates in the equatorial system, but I still wonder whether there's an easier way to do this; All I need would be the longitude of equinoxes/solstices (assuming the inclination of the orbit is 0, similar to the longitude of periapsis) of various planets and rotating the axis accordingly.

[![Earth at vernal equinox in my model](https://i.sstatic.net/BHWVPkZz.png)](https://i.sstatic.net/BHWVPkZz.png)

**Tags:** solar-system, equinox, axial-tilt
> **Comments:**
> **username_1**: You may be interested in the answer to this question: https://physics.stackexchange.com/questions/661180/where-i-can-find-obliquity-direction especially the linked PDF: https://aa.usno.navy.mil/downloads/reports/Archinaletal2011a.pdf  
> **username_1**: The comments on this question, though, seem most helpful. Especially the last one which gives you an API call you can make to get the vector from a planet's center to its north pole: https://astronomy.stackexchange.com/questions/58099/how-to-get-the-direction-of-the-rotation-axis-of-a-celestial-body-using-jpl-hori  
> **username_0**: Guess I got the image from https://www.weather.gov/cle/seasons  
> **username_0**: @Sub6Resources Thank you for the pdf file, it appears to be a place from where the Wikipedia values were taken. Now I'm thinking of converting my model to an equatorial system, orienting the poles, and converting back to ecliptical  
> **username_2**: @AlexMB thanks! I've moved the credit back into the post itself - comments are considered temporary; moderators (or the owner) can delete them at any time, so we try to keep the important bits in the post itself. Also, I noticed "if represented by three perpendicular axis, at the vernal equinox one would point directly at the sun, the second one would be oriented along the path of the planet in orbit, and the third could be rotated to fit the axial tilt of the object" inside the image link, but it doesn't appear to the readers - did you intend for that to be a visible part of the post?  
> **username_0**: @uhoh Thank you. I guess I expected that piece to be visible but the point is conveyed regardless so it's fine  

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## 0 answers

