<p><a href="https://astronomy.stackexchange.com/a/50982/7982">My new answer to <em>Why does Venus flicker?</em></a> addresses something that I find particularly interesting; Venus can be an incredibly thin crescent at times, and even a 1 arcminute large thin ring with an edge width of only one or two arcseconds (see below).</p>
<p>This suggests to me that Venus can twinkle much more like a star than a filled-disk planet at certain times. So for example in a comment there I wrote:</p>
<blockquote>
<p>I have a strong hunch that if Jupiter were sitting right next to Venus on 12 April 2015 it would not have twinkled to the same extent.</p>
</blockquote>
<p>@ProfRob notes that it turns out that Venus was a large-ish 15 arcecond disk 75% illuminated on 12 April 2015 so &quot;crescent-twinkling&quot; wasn't the reason that Venus twinkled for the OP on that day.</p>
<p>But I'm still convinced that it's gotta be a real, measurable phenomenon if there is such a thing as a planet &quot;twinkleometer&quot; and it's been applied systematically to Venus.</p>
<p>So I'd like to ask:</p>
<p><strong>Question:</strong> Has &quot;crescent-twinkling&quot; even been demonstrated or at least calculated/predicted? Any &quot;twinkleometer&quot; data out there?</p>
<hr />
<p>For more on how Venus's dance changes distance from Earth and illuminated fraction in such a way that it's almost always between -3.8 and -4.8 magnitude, see answers to</p>
<ul>
<li><a href="https://astronomy.stackexchange.com/q/33797/7982">Venus&#39; magnitude during inferior conjunction</a></li>
</ul>
<hr />
<p>From the linked answer:</p>
<blockquote>
<p><a href="https://i.sstatic.net/23E6B.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/23E6B.jpg" alt="Phases of Venus, from https://commons.wikimedia.org/wiki/File:Phases_Venus.jpg" /></a></p>
<p><strong>above:</strong> Phases of Venus, originally from <a href="https://commons.wikimedia.org/wiki/File:Phases_Venus.jpg" rel="nofollow noreferrer">Wikimedia</a> but annotated.</p>
<p>For three times in 2004 (Feb 27, May 7, and June 8) I've taken the angular diameters of Venus from <a href="https://ssd.jpl.nasa.gov/horizons/app.html#/" rel="nofollow noreferrer">JPL's Horizons</a> and using the largest (June 8) as a calibration for the image shown the full diameter of Venus.</p>
<p>Then I've drawn a thin rectangle to eyeball the width of the bright part of the limb that would contribute most of the light. The annotated numbers (15/5, 40/3, 58/1) are the apparent diameters of the full disk and the width of the bright limb <em>in arcseconds</em>.</p>
</blockquote>

CC BY-SA 4.0
2022-11-07T21:56:03.123Z
Note: as I've commented [elsewhere](https://astronomy.stackexchange.com/posts/comments/113867): "The same localized random phenomenon in the upper atmosphere that makes an object of ~arcsec extent in 2 dimensions twinkle must also make an object of ~arcsec extent in 1 dimension twinkle, though by a somewhat lesser amount. This is inescapable physics and is not open to debate. What I've asked is if anyone has measured it and/or *formally predicted it* in a rigorous and peer-reviewed way. I've added the [resource-request] tag to the question to make that clearer."
uhoh
CC BY-SA 4.0
2024-06-17T12:57:26.700Z
This is what the "shadow bands" are before and after a total solar eclipse: https://en.wikipedia.org/wiki/Shadow_bands
Greg Miller
CC BY-SA 4.0
2024-06-17T14:59:44.447Z
@GregMiller Wow, please consider writing that up as an answer, you are absolutely right!
uhoh
CC BY-SA 4.0
2024-06-22T01:56:34.170Z
@GregMiller just fyi if no answers are posted after the bounty expires I'll probably post that as an answer myself because it's pretty clearly a good answer. I won't accept it though, because I'm still holding out for "twinkleometer data for Venus". In the mean time, please consider writing that answer yourself.
uhoh
CC BY-SA 4.0
2024-06-22T02:30:31.410Z
@GregMiller just fyi "the bounty expires in 21 hour..." plus an additional 24 hour invisible [grace period](https://space.meta.stackexchange.com/a/878/12102)
uhoh
CC BY-SA 4.0
2024-06-22T19:23:19.607Z
If someone is up for fleshing that out into a full answer, please go for it.
Greg Miller
<observational-astronomy><amateur-observing><venus><atmospheric-effects><resource-request>
Has "crescent-twinkling" even been demonstrated or at least calculated/predicted? Any "twinkleometer" data for Venus out there?
uhoh
# Has "crescent-twinkling" even been demonstrated or at least calculated/predicted? Any "twinkleometer" data for Venus out there?

(Asked by: username_0 on 2022-11-07)

[My new answer to *Why does Venus flicker?*](https://astronomy.stackexchange.com/a/50982/7982) addresses something that I find particularly interesting; Venus can be an incredibly thin crescent at times, and even a 1 arcminute large thin ring with an edge width of only one or two arcseconds (see below).

This suggests to me that Venus can twinkle much more like a star than a filled-disk planet at certain times. So for example in a comment there I wrote:

> I have a strong hunch that if Jupiter were sitting right next to Venus on 12 April 2015 it would not have twinkled to the same extent.

@ProfRob notes that it turns out that Venus was a large-ish 15 arcecond disk 75% illuminated on 12 April 2015 so "crescent-twinkling" wasn't the reason that Venus twinkled for the OP on that day.

But I'm still convinced that it's gotta be a real, measurable phenomenon if there is such a thing as a planet "twinkleometer" and it's been applied systematically to Venus.

So I'd like to ask:

**Question:** Has "crescent-twinkling" even been demonstrated or at least calculated/predicted? Any "twinkleometer" data out there?

---

For more on how Venus's dance changes distance from Earth and illuminated fraction in such a way that it's almost always between -3.8 and -4.8 magnitude, see answers to

* [Venus' magnitude during inferior conjunction](https://astronomy.stackexchange.com/q/33797/7982)

---

From the linked answer:

> [![Phases of Venus, from https://commons.wikimedia.org/wiki/File:Phases_Venus.jpg](https://i.sstatic.net/23E6B.jpg)](https://i.sstatic.net/23E6B.jpg)
>
> **above:** Phases of Venus, originally from [Wikimedia](https://commons.wikimedia.org/wiki/File:Phases_Venus.jpg) but annotated.
>
> For three times in 2004 (Feb 27, May 7, and June 8) I've taken the angular diameters of Venus from [JPL's Horizons](https://ssd.jpl.nasa.gov/horizons/app.html#/) and using the largest (June 8) as a calibration for the image shown the full diameter of Venus.
>
> Then I've drawn a thin rectangle to eyeball the width of the bright part of the limb that would contribute most of the light. The annotated numbers (15/5, 40/3, 58/1) are the apparent diameters of the full disk and the width of the bright limb *in arcseconds*.

**Tags:** observational-astronomy, amateur-observing, venus, atmospheric-effects, resource-request

> **Comments:**
> **username_0**: Note: as I've commented [elsewhere](https://astronomy.stackexchange.com/posts/comments/113867): "The same localized random phenomenon in the upper atmosphere that makes an object of ~arcsec extent in 2 dimensions twinkle must also make an object of ~arcsec extent in 1 dimension twinkle, though by a somewhat lesser amount. This is inescapable physics and is not open to debate. What I've asked is if anyone has measured it and/or *formally predicted it* in a rigorous and peer-reviewed way. I've added the [resource-request] tag to the question to make that clearer."  
> **username_1**: This is what the "shadow bands" are before and after a total solar eclipse: https://en.wikipedia.org/wiki/Shadow_bands  
> **username_0**: @GregMiller Wow, please consider writing that up as an answer, you are absolutely right!  
> **username_0**: @GregMiller just fyi if no answers are posted after the bounty expires I'll probably post that as an answer myself because it's pretty clearly a good answer. I won't accept it though, because I'm still holding out for "twinkleometer data for Venus". In the mean time, please consider writing that answer yourself.  
> **username_0**: @GregMiller just fyi "the bounty expires in 21 hour..." plus an additional 24 hour invisible [grace period](https://space.meta.stackexchange.com/a/878/12102)  
> **username_1**: If someone is up for fleshing that out into a full answer, please go for it.  

---

## 0 answers

