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points by cperciva 3 days ago | 0 comments

The hard part came next. Larsen spent about 45 hours layering the individual photos – each of which contained about 25 satellites – over one another, using Adobe Photoshop. Much of the time was spent painstakingly erasing stars, to reveal the satellites.

This is less an "image of our satellite-choked night skies" and more "a completely mendacious image produced using Photoshop".

[–] happytoexplain 3 days ago

You are being uncharitable. There is nothing misleading about this, or any other, nightsky timeseries image. It claims to show the paths of satellites over 2 hours, and that's what it does. You have to edit things like this to reveal the signal and keep relatively constant elements from overwhelming the result. Astronomers do this exact same thing (erasing things that obscure the subject over time).

Even if I were to be as charitable as possible to your interpretation, "mendacious" is way too strong a word, and implies an unreasonable bitterness.

[–] fooker 3 days ago

No it is correct. I dabble in astrophotography.

The purpose of stacking hundreds of photos is to get rid of noise and unwanted trails like this.

The effort involved here is to go out of your way to do the exact opposite, specifically make sure things that are in a single exposure show up in the stack.

[–] ryandvm 3 days ago

Somehow you also seem to be missing the point.

You stack photos to enhance clarity and remove noise. Your work is not "mendacious".

But what you are removing is still data - and as you can see, some people find it to be very interesting.

[–] fooker 3 days ago

The issue is not with the fact that it is data, it is the fact we are collapsing two dimensions in this projection. First the time spread to a moment, and then 3D to 2D.

You can make data say anything by doing that.

[–] jebarker 3 days ago

I have no problem with the image and it illustrates a real phenomena. There is something slightly misleading about it though: if you point a camera in the same direction for 2 hours, take many images and then layer the images you wouldn't have a static star background like is shown here. You'd only get that star background if you used a star tracker and kept pointing at the same place in the night sky but then the foreground would be changing.

[–] boxed 3 days ago

If you do the exact opposite then? You take a very long exposure and you mask away the satellite trails and post the image as "image of how the satellites don't pollute the sky".. that's the exact same thing in reverse.

Both can't be non-misleading right?

[–] ImPostingOnHN 3 days ago

> You have to edit things like this to reveal the signal

In this case, it seems like a desired noise was selectively amplified above signal level to portray an artificially low signal-to-noise ratio, with the article concluding "look at all this noise!"

Still a really neat picture though. Well done. I'm considering buying a print.

I also wonder if knowledge of a star map is sufficient to somehow automatically mask out the stars as the earth rotates, and let the trails show through with less effort, vs masking each trail.

[–] Aurornis 3 days ago

The image itself is interesting, but the context in which it’s presented in this article is dishonest.

The headline is the worst offender, saying that the skies are “choked” with satellites.

The headline is misleading. The photo alone is interesting with the right context.

[–] wat10000 3 days ago

The guy who actually made the image seems to just think it's cool: "I knew if I carried on it would look even better and more impressive in terms of satellite numbers."

But the framing from others is terrible. "Who gave anyone permission do this?" Um, every single satellite ever launched has gone through government approvals. Sorry if you didn't start paying attention to the world of space flight until it ruined your attempt at photography, but that's on you.

[–] wolvoleo 3 days ago

There's another point: most of these satellites by far have been approved by the US, nobody else had any say in them. Right now the way it works is that approval is granted by the launching nation only.

As it clearly affects the whole world there should be some kind of international body governing it IMO. But I doubt that will happen because most nations are instead racing to get similar swarms of satellites up.

[–] wat10000 3 days ago

Most countries are party to the Outer Space Treaty, which specifically sets it up that way. An actual international organization would probably make sense now that space activity is ramping up so much, but it's not as if the current state of things is an accident the way "Who gave anyone permission do this?" implies.

[–] bix6 3 days ago

lol what. Regular citizens don’t get a say on satellites and many would prefer we didn’t put so many up. “National Security” will trump any citizen concerns every time.

[–] pintxo 3 days ago

To be fair, the majority of satellites now seems to exist because "money" will trump any citizen concerns every time.

[–] bix6 3 days ago

Agreed, I should’ve added that as the other overriding case

[–] wat10000 3 days ago

In other words, millions of people not only want those satellites to be there, but are willing to part with some of their hard-earned cash to make it happen.

This isn't some nefarious plot to manipulate the market or irradiate all the gold in Fort Knox or something. That scare-quoted "money" comes from providing useful services to people who want to pay for them. Yes, it turns out that millions of people wanting high-speed communication for their rural homes trumps people who get angry that they have to run their astrophotography through some software.

[–] bix6 3 days ago

Sorry which regular rural people are parting with their cash to launch satellites?

[–] wat10000 3 days ago

Not sure how you saw "government" and read it as "regular citizens," but do go back and read it again.

[–] bix6 3 days ago

Exactly. The regular citizens don’t get to participate in the decision.

[–] wat10000 3 days ago

Are we suddenly acting surprised at the concept of representative government?

I don't understand what people actually want to happen here. Part of living on a planet with eight billion other people is dealing with the fact that some of them are going to do things you don't like. Governments, treaties, and international organizations are how we manage it. I understand if people disagree with the specific process that's in place for these things, or disagree with the decisions that get made, but they're acting like there isn't any process, or they somehow deserve to be personally consulted as part of it.

[–] sega_sai 3 days ago

These are actual images from a telescope with no photoshop: https://noirlab.edu/public/images/iau-ann19035a/ https://noirlab.edu/public/images/iotw1946a/

The image in the original post is not too far from what you get with an actual telescope.

[–] bix6 3 days ago

The point of the image is to make a point. Art is provocative. Our skies are choked as anyone who makes Astro images will tell you.

[–] Aurornis 3 days ago

> Art is provocative

The misleading part is that readers don’t see that it’s provocative art until you carefully read the details. It’s presented like documentary evidence of what the problem looks like.

The photographer might not have intended it this way, but the writers of this post took advantage of that.

[–] bix6 3 days ago

The first sentence literally says it’s a multi image composite so…

[–] Aurornis 3 days ago

That’s not the misleading part. You don’t need an explanation to see that it’s a composite.

The misleading part is where he edited out the stars by hand.

> Much of the time was spent painstakingly erasing stars, to reveal the satellites.

The photographer wasn’t misleading. He made a cool photo. The headline is misleading.

[–] happytoexplain 3 days ago

There's nothing misleading about removing light sources to reveal other light sources. You're speaking as though they erased all the sky's stars. The image is full of stars. This is petty.

[–] Aurornis 3 days ago

I’m quoting the article where the photographer erased the stars from the frames:

> Much of the time was spent painstakingly erasing stars, to reveal the satellites.

These aren’t my words. It’s what the article says!

The final image appears to have a frame of stars added for effect, but they are dots rather than arcs because they’re from a single exposure. The satellite trails are a composite of all of the images, with the stars removed.

[–] bix6 3 days ago

Do you understand how composite images work and why they are used?

[–] hparadiz 3 days ago

I really like the photo and what it represents. We're growing as a civilization and I think that's beautiful.

[–] bix6 3 days ago

Meanwhile I’d like to be able to enjoy the stars without Elon’s shit in my face. Can’t wait for the Coca Cola advertisements some day.

[–] vlyan 3 days ago

le heckin' wholesome EU wants to do the same thing.

[–] hparadiz 3 days ago

The rest of us enjoy having high speed internet globally.

[–] happytoexplain 3 days ago

"Rest of us" is not a reasonable phrase here. You do not speak for the global population. It's not everybody vs bix6.

[–] Kevin_Flynn 3 days ago

It did say he was a photographer, not an astronomer.

Surely an astronomer would have software for this that would produce a more accurate picture.

[–] misnome 3 days ago

Almost any astronomy processing software does this for free, because when you stack a whole load of images it rejects outlier pixels (e.g. a trail present on only one image out of hundreds).

It then usually gives you an image of both the combined success, and an image of just those pixels that were rejected. So, this.

[–] cperciva 3 days ago

An astronomer would presumably not erase the stars.

[–] Kevin_Flynn 3 days ago

I was thinking the field of astronomy would need to survey the satellites, in order to make sure it doesn't interere with any of their observations of the stars.

So, they would erase the stars, but only to create a satellite mask, generally speaking.

[–] misnome 3 days ago

Actually, this is pretty common for non-scientific astrophotography! Erase Stars -> Edit background and stars colour, contrast etc separately -> Recombine!

[–] SiempreViernes 3 days ago

Why not? Stars are boring, the cool things are galaxies.

[–] cgriswald 3 days ago

Perhaps ironically there are times when astronomers “erase” galaxies. Erasing things is routine to get at the things you want.

[–] ryandvm 3 days ago

I don't understand. Are you laboring under the impression that the artist is trying to convince people that this is what the night sky looks like at any given moment? What even are you upset about?

[–] ktm5j 3 days ago

The photographer was completely transparent about how the image was produced and what it means.. how you manage to color this as dishonest is beyond me.

[–] 38295gksnf9588 3 days ago

It’s called art.

[–] jpardoe 3 days ago

Has he not heard of AI?