The train that crossed Leiden’s sky

The spreading train · 28 May 2019 — Marco Langbroek / SatTrackCam Leiden (Cospar 4353)
Event image. A separate one-second photograph acquired on 28 May 2019 at 21:54:51 UT, as labelled in the original margin. Marco Langbroek used a Canon EOS 60D and Samyang 85 mm f/1.4 lens at ISO 1600. Satellite motion produces short trails; he describes successive flares near Corona Borealis. This is four days after the 24 May recording, not a frame from that film. Native 1502 × 1002 publisher JPEG retained byte-for-byte, including timing, credit and camera labels; no added marks or enlargement.
Photographer’s published permission for his own imagery used for scientific or educational purposes with source acknowledgement. Used here in an educational case study; this is not a general commercial or advertising licence.
· Original image source · Image licence

Before the first Starlink train crossed the Netherlands, an independent satellite observer had calculated where to look. Watch his actual recording and examine a separately dated photograph as the tightly packed lights began to spread.

World: Earth
Location: Netherlands
Case date or period: 24 May 2019 UTC · separate photograph 28 May

The prediction preceded the photograph

Marco Langbroek posted an estimated initial Starlink orbit to SeeSat-L on 23 May 2019, before the planned launch. The calculation assumed a 02:30 UTC launch and warned that an early European pass would occur in deep twilight. This is a useful first-generation research record: the observer did not identify a mysterious train only after seeing publicity about it. He prepared a search from the announced orbit and launch window. The estimate nevertheless remained a prediction; it was not a catalogue solution fitted to every individual satellite or a guarantee that the train would arrive at exactly the calculated second.

An actual pass over Leiden

In his 25 May account, Langbroek dates the recorded pass to approximately 22:55 UTC on 24 May, less than a day after launch. He saw two faint flashing objects before the tightly grouped train entered his camera’s field. The predicted sky track was close, while the objects arrived around three minutes early. This comparison links a visual event to a known deployment with an explicit prediction error. For readers using Netherlands local time, the UTC date crosses midnight: 22:55 UTC 24 May is 00:55 CEST 25 May. The blog publication date and local calendar date therefore should not replace the camera’s stated UTC date.

What the camera counted

Langbroek identifies a WATEC 902H low-light surveillance camera and a Canon 50 millimetre lens at f/1.8, recording through partly cloudy sky. He counted at least 56 objects in the original video. That count is an observation bound, not a claim that every one of the 60 launched spacecraft was separately resolved. He expected the objects to spread as their orbits changed. The film records a transient clustered arrangement soon after deployment, not the finished operational constellation. Its source remains the observer’s own embedded video; animations of an orbit or clips from other countries are different products.

A separate later view tests the transient picture

Langbroek’s 30 May post presents an actual photograph from the evening of 28 May, acquired with a Canon EOS 60D and an 85 millimetre lens. He describes the train as already dispersing and objects flaring successively near Corona Borealis. This is valuable comparison evidence precisely because it is separately dated and uses another acquisition method. It should not be presented as a still from the 24 May movie or as another angle of the same instant. The changing spacing and brightness also caution against using one memorable formation as a fixed visual template for all later satellite reports.

The investigation widened beyond identification

The follow-up also examined what the planned constellation would mean for the orbital population. Langbroek distinguished current tracked objects from catalogue entries accumulated since 1957, including objects that had already re-entered. His figures were a historical tally and projection based on 2019 plans, not today’s satellite inventory. This wider analysis explains why the spectacular recording mattered to observers: identifying satellites did not settle concerns about their visibility, tracking or the changing night sky. Keep the evidence classes separate—the film documents one pass, the later photograph documents another, and population diagrams express a dated analysis of possible deployment scale.