<p>Completely imperceptible except to instruments.</p>
<p><a href="https://www.space.com/buck-moon-penumbral-lunar-eclipse-july-2020-explained.html" rel="nofollow noreferrer">Space.com reports</a></p>
<blockquote>
<p>In general, most people don't notice the penumbral shadow projected on the moon until at least 70% of its diameter is covered. Some people who have very acute vision and better-than-average perception might notice an ever-so-slight shading when only 50% of the moon is inside the penumbra.</p>
</blockquote>
<p>As your image shows, this is a lot less than 50%. Nothing will be observed by the naked eye.  &quot;Visible&quot; in your first source only means &quot;the moon will be above the horizon at this time&quot;. It doesn't mean you will be able to see a change or dimming of the moon.</p>

CC BY-SA 4.0
2020-07-04T10:35:04.577Z
2020-07-04T10:35:04.577Z
James K
<p>Wikipedia's <a href="https://en.wikipedia.org/wiki/July_2020_lunar_eclipse#Visibility" rel="nofollow noreferrer">July 2020 lunar eclipse; Visibility</a> says:</p>
<blockquote>
<p><strong>It will be visible</strong> from some parts of North America during moonrise, South and North America, the extreme part of Namaqua Land in South Africa and Western Africa (completely visible), and in southwestern Europe, New Zealand, some parts of The Pacific Ocean, Central, East Africa (except Somalia, Djibouti, Eritrea and a strip of North Eastern Sudan,Egypt and Ethiopia) and some parts of North Africa and some parts of The Indian Ocean during moonset.</p>
</blockquote>
<p>But on the sidebar there is an image that shows <em>the outer edge</em> of the penumbra cutting across the center of the Moon at maximum, which means half of the Moon will be full brightness and the other have only partially shadowed by the Earth.</p>
<p><strong>Question:</strong> How much darker with the eclipsed half of the Moon get at maximum? Just how &quot;imperceptible&quot; will the 4-July-2020 penumbral lunar eclipse really be?</p>
<hr />
<p><a href="https://en.wikipedia.org/wiki/File:Lunar_eclipse_chart_close-2020Jul05.png" rel="nofollow noreferrer">Source</a> and caption in the main Wikipedia article:</p>
<blockquote>
<p>The moon will imperceptibly dim as it passes through the Earth's southern penumbral shadow</p>
</blockquote>
<p><a href="https://i.sstatic.net/ZhM61.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/ZhM61.png" alt="The moon will imperceptibly dim as it passes through the Earth's southern penumbral shadow" /></a></p>

<amateur-observing><lunar-eclipse><brightness>
How imperceptible will the 4-July-2020 penumbral lunar eclipse be?
uhoh
# How imperceptible will the 4-July-2020 penumbral lunar eclipse be?

(Asked by: username_0 on 2020-07-04)

Wikipedia's [July 2020 lunar eclipse; Visibility](https://en.wikipedia.org/wiki/July_2020_lunar_eclipse#Visibility) says:

> **It will be visible** from some parts of North America during moonrise, South and North America, the extreme part of Namaqua Land in South Africa and Western Africa (completely visible), and in southwestern Europe, New Zealand, some parts of The Pacific Ocean, Central, East Africa (except Somalia, Djibouti, Eritrea and a strip of North Eastern Sudan,Egypt and Ethiopia) and some parts of North Africa and some parts of The Indian Ocean during moonset.

But on the sidebar there is an image that shows *the outer edge* of the penumbra cutting across the center of the Moon at maximum, which means half of the Moon will be full brightness and the other have only partially shadowed by the Earth.

**Question:** How much darker with the eclipsed half of the Moon get at maximum? Just how "imperceptible" will the 4-July-2020 penumbral lunar eclipse really be?

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[Source](https://en.wikipedia.org/wiki/File:Lunar_eclipse_chart_close-2020Jul05.png) and caption in the main Wikipedia article:

> The moon will imperceptibly dim as it passes through the Earth's southern penumbral shadow

[![The moon will imperceptibly dim as it passes through the Earth's southern penumbral shadow](https://i.sstatic.net/ZhM61.png)](https://i.sstatic.net/ZhM61.png)

**Tags:** amateur-observing, lunar-eclipse, brightness


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## 1 answers

### Answer by username_1 on 2020-07-04. Score: 3 | Accepted answer

Completely imperceptible except to instruments.

[Space.com reports](https://www.space.com/buck-moon-penumbral-lunar-eclipse-july-2020-explained.html)

> In general, most people don't notice the penumbral shadow projected on the moon until at least 70% of its diameter is covered. Some people who have very acute vision and better-than-average perception might notice an ever-so-slight shading when only 50% of the moon is inside the penumbra.

As your image shows, this is a lot less than 50%. Nothing will be observed by the naked eye. "Visible" in your first source only means "the moon will be above the horizon at this time". It doesn't mean you will be able to see a change or dimming of the moon.


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