SpaceX’s unorthodox card-dealing launch of 60 Starlink broadband satellites has led to into an unusual viewing opportunity for skywatchers — and an occasion to wonder about the impact of such mega-constellations on the natural night sky.

A video captured by satellite-watcher Marco Langbroek in the Netherlands sums up the awe. “I could not help shouting ‘OAAAAAH!!!!’ he wrote on his SatTrackCam Leiden blog. “Here is the video I shot, be prepared to be mind-blown!”:

It didn’t take long for Langbroek and other skywatchers to work out the coordinates for the long train of satellites, and to plug those coordinates into online satellite-pass calculators such as CalSky. On Twitter, David Dickinson, author of “The Universe Today Ultimate Guide to Viewing the Cosmos,” started doling out location-specific sighting predictions based on the Orbitron satellite-tracking program.

CalSky automatically picks up your coordinates for satellite sightings, but for those in the Seattle area, the best time to look for the Starlink train passing by tonight is likely to be in the range of 10:50 to 11:10 p.m. PT, going from southwest to northeast. That’s a liberal stretch of time that accounts for a range of locations (say, Port Townsend vs. North Bend), plus uncertainties in the orbital estimates.

There are other passes overnight at around 12:30, 3:50 and 5:20 a.m. PT. The brightness of the satellites is a question mark. Some say they can be seen with the naked eye, while others advise scanning with binoculars. A lot depends on how the satellites pick up the glint of the sun after dusk or before dawn. Tonight Langbroek reported that the satellite train wasn’t as bright as it was the night before.

Speaking of brightness, astronomers and SpaceX fans have already begun the debate over the prospect of having thousands of broadband-beaming satellites in low Earth orbit. The 60 satellites launched this week merely represent the beginning of a campaign aimed at launching as many as 11,000 such spacecraft. And that’s just for SpaceX’s Starlink system. Thousands more could go into orbit for the constellations being contemplated by OneWeb, Telesat, LeoSat Enterprises and Amazon’s Project Kuiper.

Last year, Rocket Lab came in for some grief from astronomers for sending up its “mirror-ball” Humanity Star satellite for a few months of twinkle time in the night sky. This week’s Starlink spectacle renewed the discussion over potential interference with astronomical observations. Even SpaceX CEO Elon Musk joined in:

I know people are excited about those images of the train of SpaceX Starlink satellites, but it gives me pause. They’re bright, and there are going to be a lot of them. If SpaceX launches all 12,000, they will outnumber stars visible to the naked eye. — Alex Parker (@Alex_Parker) May 25, 2019

Not a single one will be visible at night. Just near dusk or dawn, which are not good observing times anyway. Also, only a handful will be around at any given location. It's just not a problem. — Daniel Cincunegui (@danielcincu) May 25, 2019

Precisely, sats will be in darkness when stars are visible — Elon Musk (@elonmusk) May 25, 2019

I get that, but I see ISS ALL THE TIME at night and it has a lower altitude. — Jim McPherson (@mcjamez) May 25, 2019

ISS is extremely gigantic & has lights — Elon Musk (@elonmusk) May 25, 2019

Hate to disagree with @elonmusk, but: that is true in wintertime, but not in summertime. Then, with altitudes at 550 km, they are visible throughout the night at middle latitudes like Europe. Just like they were last night:https://t.co/xChLDH32uk — Dr Marco Langbroek (@Marco_Langbroek) May 25, 2019

I’m firmly in the ‘i think they’ll be spaced out enough it won’t really matter’ camp, but that is not true. Saw them last night at 12:10am in Chicago. (4 hours after sunset) https://t.co/8UkGG8haym — 📸Trevor Mahlmann (@TrevorMahlmann) May 25, 2019

I’ll try to do a sunlit temporal and spatial analysis tomorrow. I’m guessing we won’t like the number. — C. G. Niederstrasser (@RocketScient1st) May 25, 2019

In any case, the Starlink satellites shouldn’t be bunched up for long. SpaceX’s plan calls for each satellite to raise its orbit from the deployment altitude of 440 kilometers (273 miles) to the operational altitude of 550 kilometers (342 miles). That happens on a timed basis, every 90 minutes. The idea is that as each satellite raises its orbit, it lags behind the rest of the chain.

Within just a few days, the tightly spaced “train” will turn into a dispersed chain that girdles the globe. And once that happens, chances are that skywatchers and sky-worriers alike will turn their attention to the next batch of Starlink satellites.

Update for 3:34 a.m. PT May 27: After a couple of days of debate in the Twitterverse, Musk said steps would be taken to minimize the impact of the Starlink satellites’ shine on astronomical observations:

Any thoughts on starlink satellites causing space debris and lighting polluting the sky according to what some people are saying? — Varun Ramesh (@varunversion1) May 27, 2019

There are already 4900 satellites in orbit, which people notice ~0% of the time. Starlink won’t be seen by anyone unless looking very carefully & will have ~0% impact on advancements in astronomy. We need to move telelscopes to orbit anyway. Atmospheric attenuation is terrible. pic.twitter.com/OuWYfNmw0D — Elon Musk (@elonmusk) May 27, 2019

I am all for Starlink for the many potential benefits it may bring, but I think you may be downplaying the potential for disruption. Of those ~5000 satellites in orbit, maybe 800-1000 are in LEO. Way too early to jump to conclusions but you may want to dive a bit deeper. — Eric Ralph (@13ericralph31) May 27, 2019

If we need to tweak sat orientation to minimize solar reflection during critical astronomical experiments, that’s easily done. Most orbital objects are close to Earth btw, as shown by this NASA density map. https://t.co/83MwIZAEP6 pic.twitter.com/NllMXregRg — Elon Musk (@elonmusk) May 27, 2019

It seems that radio astronomers also have concerns about the RF band(s) Starlink operates on. I’m totally ignorant as to how these work, but are there a range of frequencies to choose from? Is it possible to minimize disruption when passing over arrays? — Stephen Bates 🚀🚀🚀🌑🔭🛰 (@GoForStaging) May 27, 2019

Yes, already planned. We avoid use of certain lower Ku frequencies specifically for radio astronomy. — Elon Musk (@elonmusk) May 27, 2019

If they help billions of people in remote locations inexpensively access the internet, it's a price I'd be willing to pay. — Fraser Cain (@fcain) May 27, 2019

Exactly, potentially helping billions of economically disadvantaged people is the greater good. That said, we’ll make sure Starlink has no material effect on discoveries in astronomy. We care a great deal about science. — Elon Musk (@elonmusk) May 27, 2019

But if you can throw up a few Starlink-chassis space telescopes, I'm sure that'll smooth things over with the astro community. Especially since they'd be able to return the data quickly via… Starlink. — Fraser Cain (@fcain) May 27, 2019

Would love to do exactly that — Elon Musk (@elonmusk) May 27, 2019

@elonmusk Please see if there are ways to reduce reflected light downwards from the later batches of Starlink satellites, as they seems to be "more shiny/higher albedo" than others. Maybe some coatings/extra mirrors would help. Thanks! — Cosmic Penguin (@Cosmic_Penguin) May 27, 2019

Agreed, sent a note to Starlink team last week specifically regarding albedo reduction. We’ll get a better sense of value of this when satellites have raised orbits & arrays are tracking to sun. — Elon Musk (@elonmusk) May 27, 2019

As the satellites disperse and reorient their solar arrays, they become less visible. I finally got a chance to see the remnants of the Starlink train on Monday morning, thanks to clearing skies over the Seattle area. Through a binoculars, I could make out four bright points of light and a smattering of lesser lights, proceeding eastward as predicted by the Calsky, N2YO and CMDR2 websites. Keep checking these and other satellite-tracking sites for future sighting opportunities.