<h1>A nightmare for star hopping</h1>
<p>I can only speak as an amateur astronomer with a 10-inch Dobsonian.</p>
<p>My telescope has no GOTO or tracking, so if I want to find something interesting in the sky, I have to use <a href="https://en.wikipedia.org/wiki/Star_hopping" rel="noreferrer">star hopping</a>:</p>
<ul>
<li>taking bright stars (up to ~mag 5) as reference points, I point the finder in the approximate direction.</li>
<li>through the finder, I can see dimmer stars (up to ~mag 9) and use them as reference to point the telescope even more accurately</li>
<li>through the eyepiece with the appropriate magnification, I can find the desired object (up to ~mag 12).</li>
</ul>
<p>This process works really well, and if I know the sequence, I can usually find dim objects in less than 15 seconds, even from my light-polluted suburban skies.</p>
<p>In order to practice star hopping, I need to see the star patterns, I need to recognize them, and I need to memorize them. Having <em>42000</em> mag 6.5 satellites in the sky will make those 3 steps <em>really</em> hard.</p>
<p>For reference, here are 42000 <a href="https://stackoverflow.com/a/44164075/6419007">evenly distributed points on a sphere</a>, between latitude 60°S and 60°N:</p>
<p><a href="https://i.sstatic.net/Oi7oc.png" rel="noreferrer"><img src="https://i.sstatic.net/Oi7oc.png" alt="enter image description here" /></a></p>

CC BY-SA 4.0
2021-04-21T21:16:38.283Z
At such a low altitude, Starlink satellites will be moving roughly [0.5 to 1.4 degrees *per second*](https://astronomy.stackexchange.com/a/35967/7982) (also [here](https://astronomy.stackexchange.com/a/33590/7982) and [here](https://astronomy.stackexchange.com/a/33935/7982)). I don't see how one could confuse something moving that fast with a star. And of course chances are low that one will pass through your finder scope's FOV during your star hopping.
uhoh
CC BY-SA 4.0
2021-04-22T03:26:36.397Z
@uhoh when I know the pattern, I really don't need more than a very quick glance to recognize it. It's just an instant look, so angular velocity of the object doesn't play a role. A bright point is there, and shouldn't be. So I need a double take, and then realize the problem. Without horizon as reference, it's also less easy to recognize a moving object. It already happened to me with iridiums, ISS and starlinks. I regularly see satellites in the finder. With 15 times the density, it would be harder to memorize clean patterns.
Eric Duminil
CC BY-SA 4.0
2021-04-22T03:29:46.910Z
That's amazing! It's been more decades than I care to admit since I've actually looked through a finder scope :-)
uhoh
CC BY-SA 4.0
2021-04-21T14:35:02.687Z
2021-04-21T14:35:02.687Z
Eric Duminil
<p>Satellites just add moving lights to the sky, they do not obscure stars. However, some may find that disrupting their view of what a sky should look like.</p>
<p><a href="https://en.wikipedia.org/wiki/Apparent_magnitude" rel="noreferrer">The visual magnitude</a> of starlink satellites is <a href="https://arxiv.org/ftp/arxiv/papers/2101/2101.00374.pdf" rel="noreferrer">about 5.92 at zenith</a>, and usually darker (but also sometimes brighter). <a href="https://arxiv.org/abs/2003.07251" rel="noreferrer">The new darker satellites are about 0.77 magnitudes fainter</a>. This is in the lower range for naked eye vision under good conditions.</p>
<p>Light pollution is likely to make the satellites invisible to most people, since they already cannot see much of the sky. You need to be <a href="https://en.wikipedia.org/wiki/Bortle_scale" rel="noreferrer">outside suburban skies on the Bortle scale to be able to notice them.</a> So if you are concerned with the aesthetics of the sky, city light pollution is a far, far greater problem.</p>

CC BY-SA 4.0
2021-04-20T21:29:40.537Z
I think it's a slippery slope, though. Light pollution is indeed a *huge* problem, but no single light source is problematic : it's the sheer quantity of small light sources which is the problem. And people keep adding them and the night skies are only getting worse and worse. Launching 10 satellites to LEO? Not a problem for visual astronomy. But launching *40000* satellites?
Eric Duminil
CC BY-SA 4.0
2021-04-21T08:39:10.277Z
@EricDuminil the major problem is not the light per sé, but the fact that professional observation can be hard to be elaborated.
Alchimista
CC BY-SA 4.0
2021-04-21T09:19:06.757Z
Comment was intended to the comment :)
Alchimista
CC BY-SA 4.0
2021-04-20T13:04:22.190Z
2021-04-20T13:04:22.190Z
Anders Sandberg
<p>There is some discussion (and there are some <a href="https://astronomy.stackexchange.com/questions/43471/why-is-starliink-polluting-the-night-sky-a-big-concern-if-we-have-space-telescop">questions</a> on this site) about the impact of Starlink on observational astronomy. I am not an astronomer, but I am amazed by the beauty an immensity of the night sky.</p>
<p>Must I be concerned, from an aesthetical point of view, that Starlink will change the night sky that I and countless people before me have admired? For example, will there be less stars visible to the naked eye, or will the night sky be defaced by a myriad of artificial light sources?</p>
<p>For background: <a href="https://en.wikipedia.org/wiki/Starlink" rel="noreferrer">Starlink</a> is a commercial project by SpaceX, a private company, that seeks to launch thousands of small satellites into the earth's orbit.</p>

CC BY-SA 4.0
2021-04-20T09:57:01.673Z
Starlink won't obscure stars and the night sky will remain amazing as it is. But the project seems to pose problem to professional astronomers. https://astronomy.stackexchange.com/questions/43471/why-is-starlink-polluting-the-night-sky-a-big-concern-if-we-have-space-telescope
Alchimista
CC BY-SA 4.0
2021-04-20T10:01:55.093Z
@Alchimista that might be an answer if you could elaborate a bit as to what the implications visible to the naked eye are.
henning no longer feeds AI
CC BY-SA 4.0
2021-04-20T10:39:18.767Z
consider three facts 1 geometry, I am not going to calculate how much fov a starlink satellite occupies 2 they move 3 they just reflect and can be visible at specific time only.
Alchimista
CC BY-SA 4.0
2021-04-20T11:01:04.920Z
Thanks. If this were an answer, I would probably mark as accepted (depending on what else comes up).
henning no longer feeds AI
CC BY-SA 4.0
2021-04-20T16:24:54.787Z
@Alchimista amateur astrophotographers making pictures of star trails may see them as well, though I'm not sure about that.
uhoh
CC BY-SA 4.0
2021-04-20T18:41:48.130Z
@Alchimista Many people at least use binoculars to watch the skies, some also more powerful instruments. I wouldn't be so sure that the sky "remains amazing as it is" for people like me. The Starlink train *was* visible with the naked eye, and even the newer ones *are* visible with binoculars.
Polygnome
CC BY-SA 4.0
2021-04-20T19:19:26.467Z
It already is defaced
Voltage Spike
CC BY-SA 4.0
2021-04-20T20:34:10.380Z
It will probably make a hell of a mess for radio telescopes.
Matthew Whited
CC BY-SA 4.0
2021-04-21T08:32:43.903Z
@uhoh yes but it usually wanted. I've missed all launches to date.
Alchimista
CC BY-SA 4.0
2021-04-21T08:37:53.990Z
Let us stay practical. It is matter of what "deface" means. They won't obscure the stars. I am also somehow sad if plenty of artificial moving lights will populate the sky. This goes even far beyond astronomy and my feeling is certainly off topic. Basically individuals can take over something that at least look like something of all, or nobody.
Alchimista
CC BY-SA 4.0
2021-04-21T08:38:47.520Z
@Alchimista [Are there Starlink train-finding websites?](https://space.stackexchange.com/q/48032) I think I'm going to write a script based on Skyfield that draws from Celestrak. It won't update until the Starlinks get TLE's but hopefully they are getting good at assigning ID's to them quickly now.
uhoh
<night-sky><artificial-satellite><light-pollution>
Will Starlink deface the night sky?
henning no longer feeds AI
# Will Starlink deface the night sky?

(Asked by: username_0 on 2021-04-20)

There is some discussion (and there are some [questions](https://astronomy.stackexchange.com/questions/43471/why-is-starliink-polluting-the-night-sky-a-big-concern-if-we-have-space-telescop) on this site) about the impact of Starlink on observational astronomy. I am not an astronomer, but I am amazed by the beauty an immensity of the night sky.

Must I be concerned, from an aesthetical point of view, that Starlink will change the night sky that I and countless people before me have admired? For example, will there be less stars visible to the naked eye, or will the night sky be defaced by a myriad of artificial light sources?

For background: [Starlink](https://en.wikipedia.org/wiki/Starlink) is a commercial project by SpaceX, a private company, that seeks to launch thousands of small satellites into the earth's orbit.

**Tags:** night-sky, artificial-satellite, light-pollution
> **Comments:**
> **username_1**: Starlink won't obscure stars and the night sky will remain amazing as it is. But the project seems to pose problem to professional astronomers. https://astronomy.stackexchange.com/questions/43471/why-is-starlink-polluting-the-night-sky-a-big-concern-if-we-have-space-telescope  
> **username_0**: @Alchimista that might be an answer if you could elaborate a bit as to what the implications visible to the naked eye are.  
> **username_1**: consider three facts 1 geometry, I am not going to calculate how much fov a starlink satellite occupies 2 they move 3 they just reflect and can be visible at specific time only.  
> **username_0**: Thanks. If this were an answer, I would probably mark as accepted (depending on what else comes up).  
> **username_2**: @Alchimista amateur astrophotographers making pictures of star trails may see them as well, though I'm not sure about that.  
> **username_3**: @Alchimista Many people at least use binoculars to watch the skies, some also more powerful instruments. I wouldn't be so sure that the sky "remains amazing as it is" for people like me. The Starlink train *was* visible with the naked eye, and even the newer ones *are* visible with binoculars.  
> **username_4**: It already is defaced  
> **username_5**: It will probably make a hell of a mess for radio telescopes.  
> **username_1**: @uhoh yes but it usually wanted. I've missed all launches to date.  
> **username_1**: Let us stay practical. It is matter of what "deface" means. They won't obscure the stars. I am also somehow sad if plenty of artificial moving lights will populate the sky. This goes even far beyond astronomy and my feeling is certainly off topic. Basically individuals can take over something that at least look like something of all, or nobody.  
> **username_2**: @Alchimista [Are there Starlink train-finding websites?](https://space.stackexchange.com/q/48032) I think I'm going to write a script based on Skyfield that draws from Celestrak. It won't update until the Starlinks get TLE's but hopefully they are getting good at assigning ID's to them quickly now.  

---

## 2 answers

### Answer by username_7 on 2021-04-20. Score: 16 | Accepted answer

Satellites just add moving lights to the sky, they do not obscure stars. However, some may find that disrupting their view of what a sky should look like.

[The visual magnitude](https://en.wikipedia.org/wiki/Apparent_magnitude) of starlink satellites is [about 5.92 at zenith](https://arxiv.org/ftp/arxiv/papers/2101/2101.00374.pdf), and usually darker (but also sometimes brighter). [The new darker satellites are about 0.77 magnitudes fainter](https://arxiv.org/abs/2003.07251). This is in the lower range for naked eye vision under good conditions.

Light pollution is likely to make the satellites invisible to most people, since they already cannot see much of the sky. You need to be [outside suburban skies on the Bortle scale to be able to notice them.](https://en.wikipedia.org/wiki/Bortle_scale) So if you are concerned with the aesthetics of the sky, city light pollution is a far, far greater problem.

> **Comments:**
> **username_6**: I think it's a slippery slope, though. Light pollution is indeed a *huge* problem, but no single light source is problematic : it's the sheer quantity of small light sources which is the problem. And people keep adding them and the night skies are only getting worse and worse. Launching 10 satellites to LEO? Not a problem for visual astronomy. But launching *40000* satellites?  
> **username_1**: @EricDuminil the major problem is not the light per sé, but the fact that professional observation can be hard to be elaborated.  
> **username_1**: Comment was intended to the comment :)  

---

### Answer by username_6 on 2021-04-21. Score: 12

# A nightmare for star hopping

I can only speak as an amateur astronomer with a 10-inch Dobsonian.

My telescope has no GOTO or tracking, so if I want to find something interesting in the sky, I have to use [star hopping](https://en.wikipedia.org/wiki/Star_hopping):

* taking bright stars (up to ~mag 5) as reference points, I point the finder in the approximate direction.
* through the finder, I can see dimmer stars (up to ~mag 9) and use them as reference to point the telescope even more accurately
* through the eyepiece with the appropriate magnification, I can find the desired object (up to ~mag 12).

This process works really well, and if I know the sequence, I can usually find dim objects in less than 15 seconds, even from my light-polluted suburban skies.

In order to practice star hopping, I need to see the star patterns, I need to recognize them, and I need to memorize them. Having *42000* mag 6.5 satellites in the sky will make those 3 steps *really* hard.

For reference, here are 42000 [evenly distributed points on a sphere](https://stackoverflow.com/a/44164075/6419007), between latitude 60°S and 60°N:

[![enter image description here](https://i.sstatic.net/Oi7oc.png)](https://i.sstatic.net/Oi7oc.png)

> **Comments:**
> **username_2**: At such a low altitude, Starlink satellites will be moving roughly [0.5 to 1.4 degrees *per second*](https://astronomy.stackexchange.com/a/35967/7982) (also [here](https://astronomy.stackexchange.com/a/33590/7982) and [here](https://astronomy.stackexchange.com/a/33935/7982)). I don't see how one could confuse something moving that fast with a star. And of course chances are low that one will pass through your finder scope's FOV during your star hopping.  
> **username_6**: @uhoh when I know the pattern, I really don't need more than a very quick glance to recognize it. It's just an instant look, so angular velocity of the object doesn't play a role. A bright point is there, and shouldn't be. So I need a double take, and then realize the problem. Without horizon as reference, it's also less easy to recognize a moving object. It already happened to me with iridiums, ISS and starlinks. I regularly see satellites in the finder. With 15 times the density, it would be harder to memorize clean patterns.  
> **username_2**: That's amazing! It's been more decades than I care to admit since I've actually looked through a finder scope :-)  

---

