Another attempt

I’d found the website transit-finder.com last year, which takes a given location and lists the upcoming transits of the sun and moon for the International Space Station (as well as the Hubble Space Telescope and the Tiangong Space Station.) Last September I’d tried it out and did indeed see the ISS, but it came nowhere near the moon, despite the fact that we (Mr Bugg and I) made sure to be as close to the centerline of the pass as possible. I wasn’t sure what to put this down to; the site might just have been inaccurate, or the ISS might have gone through a boost in the week or so after I’d first plotted the transit. There was some support for this, in that when I went back in to confirm, a few days before the event, I noticed that both the time and the date had changed, though I might have chalked it up then to an error on my part. Still, I was wary this time around.

[Small note: Due to atmospheric drag, the ISS needs periodic rocket reboosts to maintain its orbital altitude, and these aren’t routinely scheduled because the drag is actually variable depending on conditions.]

I finally got around to trying again, yesterday evening. This time, I made sure to check the site right up until I was ready to leave, and was in place less than 30 meters from the centerline, meaning the ISS should pass right through the middle of the moon. I went with video this time around, especially since it was still daylight, and a bit hazy at that, and I wasn’t sure how clearly I’d see it. I’d synced my watch to atomic time and started the video about a minute ahead of the plotted pass. And this certainly benefits from being expanded to full-screen.

The amusing bit is, I watched the video carefully three times before I actually saw the ISS pass through; I was expecting a darker spot against the moon, or a brighter spot against the sky if the ISS was catching the sunlight adequately. I wasn’t looking up at the sky, nor at the LCD screen, when I went to stop the video – I’d checked my watch to ensure that we were well past the time of the transit, so long afterward when reviewing the video, the appearance of the plane was momentarily startling (thus I couldn’t pull up the Flightradar24 app and find out whose plane and where it was going.)

Still, this vindicated the site, since this was as close to prediction as I could confirm without looking carefully at my watch – within 30 seconds, at least, and bang-on for the location. I’d noted that the transit was only predicted to last 0.59 seconds and that’s close enough to count, too – that thing was hauling across the sky. It would be much better at night, though.

While there, I did a few photos too, mostly to nail focus.

The haze undoubtedly reduced the contrast a bit, so I’m actually lucky to have caught the ISS at all. Some time later and back home, I went out to grab a comparison shot:

This was not quite three hours later, but the apparent rotation isn’t accurate: I’d rotated the camera in the lens mount for the video so the apparent motion would traverse side-to-side, maximizing the time within the frame.

The next opportunity will be a solar transit in just two days time, so we’ll see what happens with that one. Against the sun, even with the solar filter, the shutter speed can be a hell of a lot faster, and so maybe something more than blurs can be captured in the frame. Wish me luck!