<p>The Sun's <a href="https://en.wikipedia.org/wiki/Hour_angle" rel="nofollow noreferrer">hour angle</a>, measured around the celestial equator, changes at a nearly constant rate.
The gnomon of a sundial is aligned with the polar axis to take advantage of this.
The celestial equator is oblique to the horizon except at the Earth's equator and poles.</p>

<p>The lines of azimuth converge at the observer's zenith and nadir, so the Sun's azimuth changes more rapidly near one of those points (e.g. summer midday, winter midnight) and more slowly near the horizon.
The amplitude of this fluctuation depends on the Sun's <a href="https://en.wikipedia.org/wiki/Declination" rel="nofollow noreferrer">declination</a> and the observer's geographic latitude.</p>

<p>For an observer in the tropics, on a day when the Sun passes directly overhead, its azimuth swings abruptly from 90&deg; to 270&deg; at noon.
For an observer near the north or south pole, the Sun remains near the same altitude all day, and its azimuth rate stays near the average 15&deg;/hour.</p>

CC BY-SA 4.0
2019-05-20T20:15:43.413Z
2019-05-20T20:15:43.413Z
Mike G
<p>For the past few dates, I've been observing the rotation of the earth around the sun and noticed that the azimuth of the sun doesn't vary uniformly throughout the day. The azimuth varies faster during some parts of the day, depending on the position 
<a href="https://planetcalc.com/4270/" rel="nofollow noreferrer">link</a>.</p>

<p>Why does this happen? I've been thinking about the cause, but can't come up with a proper explanation.</p>

<p><a href="https://i.sstatic.net/r2PVh.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/r2PVh.jpg" alt="enter image description here"></a></p>

<the-sun><rotation><azimuth>
Why doesn't the solar azimuth vary uniformly
Ant1
# Why doesn't the solar azimuth vary uniformly

(Asked by: username_0 on 2019-05-20)

For the past few dates, I've been observing the rotation of the earth around the sun and noticed that the azimuth of the sun doesn't vary uniformly throughout the day. The azimuth varies faster during some parts of the day, depending on the position
[link](https://planetcalc.com/4270/).

Why does this happen? I've been thinking about the cause, but can't come up with a proper explanation.

[![enter image description here](https://i.sstatic.net/r2PVh.jpg)](https://i.sstatic.net/r2PVh.jpg)

**Tags:** the-sun, rotation, azimuth

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## 1 answers

### Answer by username_1 on 2019-05-20. Score: 4 | Accepted answer

The Sun's [hour angle](https://en.wikipedia.org/wiki/Hour_angle), measured around the celestial equator, changes at a nearly constant rate.
The gnomon of a sundial is aligned with the polar axis to take advantage of this.
The celestial equator is oblique to the horizon except at the Earth's equator and poles.

The lines of azimuth converge at the observer's zenith and nadir, so the Sun's azimuth changes more rapidly near one of those points (e.g. summer midday, winter midnight) and more slowly near the horizon.
The amplitude of this fluctuation depends on the Sun's [declination](https://en.wikipedia.org/wiki/Declination) and the observer's geographic latitude.

For an observer in the tropics, on a day when the Sun passes directly overhead, its azimuth swings abruptly from 90° to 270° at noon.
For an observer near the north or south pole, the Sun remains near the same altitude all day, and its azimuth rate stays near the average 15°/hour.


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