Twinkle, twinkle, little Starlink...

Well this is worrying.

Last night, they were taking about 40 exposures of the night sky, looking towards the small and large magellanic clouds, two dwarf galaxies that neighbor the Milky Way. But during one set of those observations, 90 minutes before sunrise, the train of SpaceX’s Starlink satellites moved into view, glinting in the early morning sunlight and taking five minutes to pass across the telescope's line of sight. 

"This happened just before astronomical twilight," says Johnson. "By almost any observing standard this was still the heart of the night, exactly when you want to be taking data. And especially when you want to use every minute of observing time you get on these telescopes and these facilities."

There are several factors that could affect how much worse this will get :

• The number of satellites : "So far, SpaceX has launched just 0.14 percent of its total planned Starlink constellation.... Bassa has calculated that up to 140 satellites could be visible at any one time if all the planned satellites launch.". Doesn't specify what's meant by "visible" here, i.e. in what field of view.
• The altitude of the satellites : "The satellites were deployed in a long train at an altitude of 280 kilometers... but are in the process of being raised to their operational altitude of 550 kilometers". The higher they are, the longer they'll reflect sunlight, though they will also be fainter.
• The albedo of the satellites : "...painting future Starlink satellites black to reduce their reflectivity, although it’s not believed this was done for this latest batch – while the glinting of the large solar panels on each satellite still poses a problem."

On the second point, it would be nice to know exactly how long before twilight this was. There are detailed, credible-sounding articles saying that the satellites impact on astronomy will be minimal, but that they're visible even in full night somewhat contradicts that. So just how much astronomical night will be lost ? If it's five minutes then that's not awful (although I wonder how much this will affect flat fields also), but if it's longer then that could be a big deal. Especially for targets of opportunity, which can't be neatly scheduled to avoid inconvenient hours. Maybe painting them black will be enough, but wouldn't it be nice to test this before going full throttle ?

[Walks away angrily singing the Firefly theme tune...]

'This Is Not Cool!' - Astronomers Despair As SpaceX Starlink Train Ruins Observation Of Nearby Galaxies

In the early hours of the morning today, November 18, two astronomers checked in on their remotely operated telescope in Chile, expecting to see images of distant stars and galaxies. Instead, they saw a train of SpaceX satellites crossing the night sky, a worrying sign of what might be to come for astronomy.