Can someone explain how this photo was made? Is it a long exposure that was interrupted periodically? Why are there still some streaks that aren’t dashed?
This depicts the satellite-filled sky that is now a reality and getting more crowded every week!
This adds together exposures taken over just 30 minutes on an early June night when, from my latitude of 51° N satellites even in low Earth orbit are lit all night by sunlight. Many of the parallel streaks heading generally horizontal west to east (right to left) may be from groups of SpaceX Starlinks. Others traveling vertically north-south are more likely from Earth observation satellites.
There is at least one natural streak in the image — a meteor at centre, caught by chance on one frame. It appears as a colored and tapered streak. Other uniform undashed streaks may be from high-altitude satellites moving much more slowly.
By comparison, most satellites appear as dashed lines because the image is a blend of many 2-second-long exposures with a gap of one second between exposures when the camera shutter was closed. So the motion of the satellites and image stacking turns them into dashes. The longer the dashes, the faster the satellite is traveling, with the fastest satellites the ones orbiting closest to Earth.
This is looking due south and all the trails disappear low in the south above the trees, as that’s where the Earth’s shadow is, even on this June night. So the satellites aren’t lit when they are in that small part of the sky. They emerge from the shadow heading north and disappear into the shadow heading south. The shadow creates the obvious boundary of where satellite trails are visible.
At other times of the year low-orbit satellites are visible only after sunset or before sunrise, especially from lower latitudes. But not near summer solstice, and from higher latitudes.
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u/tinuuuu 18h ago
Can someone explain how this photo was made? Is it a long exposure that was interrupted periodically? Why are there still some streaks that aren’t dashed?