Los Angeles-based photographer Mack Murdoc recently made this amazing photo of the ISS transiting (i.e. passing across the face of) the Sun.
Murdoc was shooting with a ZWO ASI120 Monochrome camera and SOLARMAX II 90MM DOUBLE STACK telescope at a focal length of 800mm on a Orion Atlas EQ-G computerized GoTo telescope mount.
“Wow, I seriously can’t believe I got this shot,” Murdoc writes. “It amazes me that doing something like this is even possible.”
To shoot the photos, Murdoc carefully planned things out before traveling an hour into the desert in hopes of capturing an event that lasts 0.2 seconds — something that’s over faster than you can blink your eyes.
“You need to figure out when the ISS is going to pass in front of the sun and then find the exact coordinate and elevation where to line yourself up exactly with the ISS and the Sun,” Murdoc says, “[A]nd let me tell ya, you have like, half a mile of wiggle room or else you’re too far off and the ISS will just clip the side, or you can completely miss it.”
Once you figure out those details, you’ll need to travel to the correct location and get all your gear set up ahead of time to make sure everything you can control is ready.
“The space station travels at 17,500mph, so the time it takes the ISS to go from 1 side of the sun to the other is exactly .5 of a second,” Murdoc says. “With my field of view on my camera and lens, it was more like 0.2 of a second.”
When the time of the transit comes, you start firing off exposures as rapidly as you can while praying that all your calculations and preparations were correct.
“By now you’ve figured out the exact time down to the millisecond on when the ISS will cross,” the photographer says. “You start your count down, 10 – 9 – 8 – 7 -6 – 5- 4- 3- 2- 1- 0, by now you’re firing off exposures just in case it comes early or late, and you’re watching your computer screen in excitement as it blows right through your frame.”
And if you end up with an ISS solar transit composite photo like the one above, the effort will have been worth it.