<p>It is the first one, i.e. as soon as the heavenly body can be first seen. Here a definition from <a href="http://www.ga.gov.au/scientific-topics/astronomical/astronomical-definitions" rel="nofollow noreferrer">http://www.ga.gov.au/scientific-topics/astronomical/astronomical-definitions</a></p>
<blockquote>
<p>Sunrise is defined as the instant in the morning under ideal meteorological conditions, with standard refraction of the Sun's rays, when the upper edge of the sun's disk is coincident with an ideal horizon.</p>
</blockquote>

CC BY-SA 4.0
2021-01-26T08:44:55.010Z
2021-01-26T08:44:55.010Z
B--rian
<p>When you time an astronomical event, such as the moon/sun rising above the horizon, do you note the time when the the first sliver breeches the horizon or when the bottom of the moon/sun just becomes visible?</p>

<terminology><definition><sunrise><sunset>
Timing based on upper or lower part of sun/moon
Bookaholic
# Timing based on upper or lower part of sun/moon

(Asked by: username_0 on 2021-01-26)

When you time an astronomical event, such as the moon/sun rising above the horizon, do you note the time when the the first sliver breeches the horizon or when the bottom of the moon/sun just becomes visible?

**Tags:** terminology, definition, sunrise, sunset

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## 1 answers

### Answer by username_1 on 2021-01-26. Score: 2 | Accepted answer

It is the first one, i.e. as soon as the heavenly body can be first seen. Here a definition from <http://www.ga.gov.au/scientific-topics/astronomical/astronomical-definitions>

> Sunrise is defined as the instant in the morning under ideal meteorological conditions, with standard refraction of the Sun's rays, when the upper edge of the sun's disk is coincident with an ideal horizon.


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