<p>As noted in comments, at the september equinox, the sun's declination is decreasing (slightly) during the day, so the declination will be slightly higher in the morning than in the evening.</p>
<p>But the right ascension is increasing so the RA will be slightly greater in the evening.</p>

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2021-11-12T20:19:41.180Z
2021-11-12T20:19:41.180Z
James K
<p>I'm trying to solve this task:</p>
<blockquote>
<p>At what point in time of autumnal equinox day, at sunrise or sunset will
a) the declination of the Sun
b) the right ascension of the Sun
reach the maximum value?</p>
</blockquote>
<p>I'm not really sure how they change during the day and how it differs on the autumnal equinox day. Any ideas?</p>

CC BY-SA 4.0
2021-11-12T19:14:22.227Z
Not sure I understand the question. How "autumnal equinox day" is defined in this question? for  autumnal equinox is not really a day, but a specific moment where the declination = 0. and RA = 180. But FWIW, if the autumnal equinox is September equinox (for in the Southern Hemisphere is Spring) the declination is on the way down into negative territory because we are coming closer to Winter solstice at the Northern Hemisphere. , where the RA is on the rise. (as always from 0 to 359)
d_e
<the-sun><coordinate><declination><right-ascension><equinox>
At what time of the day of autumnal equinox the Sun's equatorial coordinates reach max value?
ALiCe P.
# At what time of the day of autumnal equinox the Sun's equatorial coordinates reach max value?

(Asked by: username_0 on 2021-11-12)

I'm trying to solve this task:

> At what point in time of autumnal equinox day, at sunrise or sunset will
> a) the declination of the Sun
> b) the right ascension of the Sun
> reach the maximum value?

I'm not really sure how they change during the day and how it differs on the autumnal equinox day. Any ideas?

**Tags:** the-sun, coordinate, declination, right-ascension, equinox

> **Comments:**
> **username_1**: Not sure I understand the question. How "autumnal equinox day" is defined in this question? for  autumnal equinox is not really a day, but a specific moment where the declination = 0. and RA = 180. But FWIW, if the autumnal equinox is September equinox (for in the Southern Hemisphere is Spring) the declination is on the way down into negative territory because we are coming closer to Winter solstice at the Northern Hemisphere. , where the RA is on the rise. (as always from 0 to 359)  

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## 1 answers

### Answer by username_2 on 2021-11-12. Score: 4 | Accepted answer

As noted in comments, at the september equinox, the sun's declination is decreasing (slightly) during the day, so the declination will be slightly higher in the morning than in the evening.

But the right ascension is increasing so the RA will be slightly greater in the evening.


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