<blockquote>
<p>Or is 0 degrees the direction towards the ascending node 'equinox'? Which is NOT towards the Sun on January first...</p>
</blockquote>
<p>The answer is yes, more or less. From JPL's HORIZONS, the location of the Sun at Noon Terrestrial Time on 1 Jan 2000 is, ignoring atmospheric effects, a right ascension of 18 hours, 45 minutes, and 9.36 seconds. This is nowhere close to a right ascension of zero hours (or 24 hours, same thing).</p>
<p>The right ascension of the Sun with respect to the center of the Earth is zero at the March equinox.</p>

CC BY-SA 4.0
2020-07-30T08:13:53.883Z
Where is that point on Earth, by the way?  0 degrees right ascension.... What country or ocean?  What longitude?
Kurt Hikes
CC BY-SA 4.0
2020-07-30T10:39:07.700Z
@KurtHikes The Earth rotates, nutates, and precesses. You appear to be asking how to convert between Earth-Centered Inertial and Earth-Centered Earth-Fixed coordinates.
David Hammen
CC BY-SA 4.0
2020-06-18T23:34:53.693Z
2020-06-18T23:34:53.693Z
David Hammen
<p>Is 0 degrees in the J2000 Epoch 'right ascension' is a line from Earth to the sun on January 1, 2000? Or is 0 degrees the direction towards the ascending node 'equinox'?  Which is NOT towards the Sun on January first...</p>

<observational-astronomy><coordinate><equinox>
What direction does 0° in the J2000 epoch point towards on January 1, 2000?
Kurt Hikes
# What direction does 0° in the J2000 epoch point towards on January 1, 2000?

(Asked by: username_0 on 2020-06-18)

Is 0 degrees in the J2000 Epoch 'right ascension' is a line from Earth to the sun on January 1, 2000? Or is 0 degrees the direction towards the ascending node 'equinox'? Which is NOT towards the Sun on January first...

**Tags:** observational-astronomy, coordinate, equinox


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## 1 answers

### Answer by username_1 on 2020-06-18. Score: 3 | Accepted answer

> Or is 0 degrees the direction towards the ascending node 'equinox'? Which is NOT towards the Sun on January first...

The answer is yes, more or less. From JPL's HORIZONS, the location of the Sun at Noon Terrestrial Time on 1 Jan 2000 is, ignoring atmospheric effects, a right ascension of 18 hours, 45 minutes, and 9.36 seconds. This is nowhere close to a right ascension of zero hours (or 24 hours, same thing).

The right ascension of the Sun with respect to the center of the Earth is zero at the March equinox.

> **Comments:**
> **username_0**: Where is that point on Earth, by the way?  0 degrees right ascension.... What country or ocean?  What longitude?  
> **username_1**: @username_0 The Earth rotates, nutates, and precesses. You appear to be asking how to convert between Earth-Centered Inertial and Earth-Centered Earth-Fixed coordinates.  

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