4 June 2020 ISS-Moon Transit

I discovered at the very last moment that there would be ISS-Moon transit right across my place. I had only a short time to set up a telescope and get ready. It had been quite cloudy all day, but in the last half hour before the transit the entire eastern sky cleared up. This occurred right at the full Moon, and the ISS was still lit. I watched it cross the sky, almost straight overhead. The entire pass was about 10 minutes long. In this image you can see the ISS just above the Moon, just a few seconds away from its transit.

The setup here is the portable system I put together to image the 2017 solar eclipse, a Stellarvue 102A on an iOptron CEM25P mount. This is a sweet little package that only takes a few minutes to unpack and assemble, and it runs off a small battery for hours.

Here the ISS is just crossing the Moon's limb. An interesting feature of this transit occurs because the ISS was still in sunlight (even though the Sun was below the local horizon). So instead of being silhouetted the way we usually see in images, it was actually brighter than the Moon, so appears as a bright spot, not a dark one. Look closely and you can see that the ISS is tinged blue; presumably it is reflecting back some of the Earth's light as well as the Sun's.

This is a stack of the complete sequence I shot. The gaps are a consequence of the maximum burst limit of my Canon 7D. The individual exposures are about a tenth of a second apart, 4.6 seconds beginning to end.

---