Image credit Miguel Claro
The image shows the International (ISS) silhouette while crossing the Sun´s disc The ISS completes an entire orbit around Earth each 90 minutes. Carrying on board astronauts, the large artificial satellite orbiting our planet with a width of 108.5 meters seems although very small when compared with the Solar disc with an angular size of 31.5′ is actually 29.2 times larger than the ISS in the moment of the passage. Hard to see it even with a special telescope equipped with Ha filters, only the fast video camera shutter set to an high speed frame rate could capture this rare moment that happens in a blink of an eye, as it was seen from Redondo, Dark Sky® Alqueva Reserve, Portugal, on June 6, 2021, at 13h20m11s (UT 12h20m11s) with a total duration of only 0,55 seconds.
Detailed info and technical details here: miguelclaro.com