Wesley's Tool-Box

The two biggest objects orbiting the low earth orbit, International Space Station (ISS) and the Tiangong Space Station (a.k.a. Chinese Space Station or CSS) can be seen transiting the Sun every now and then. But because their orbital characteristics are different, it's hard to see the two like that on the same day within the 200 km range. And it's much rarer for the two to be seen in front of the Sun at the same time. But earlier this month, I found out that I could see the next best thing - seeing the two make the transit from the same location within 14 minutes of each other.

The result of this observation is shown here as a multiple-frame composite. Thanks to the weather, both space stations were photographed clearly and you can make out their distinct shapes - the less dense one is Tiangong. And because the observations occurred within a short timeframe, it's easy to gauge the relative apparent size difference between each other.

Close-ups of the two space stations make this more apparent. The ISS was 53 arc-seconds wide at 521 km away, while Tiangong was 37 arc-seconds wide at 460 km away. The difference in distance shows that Tiangong's orbit is lower than that of ISS. In fact, Tiangong's nominal orbit is around 375 km, while ISS is at about 420 km.

If the ISS was observed at the same distance, it would have been 60 arc-seconds wide. This means that Tiangong, which was fully built a few months ago, is roughly 60% as wide as the ISS and much bigger than what the transit finder website claims. I think that it's showing the size of just the core module (Tianhe), not the entire structure.

Maybe if I get lucky I will be able to spot the two making the transit at the same time in the future. Until then, I'll keep looking.

Device: Nikon P1000
Settings: 3000mm - ISO 200 - 1/1000s - f/8
Filters: ICE N100000 (Neutral Density 16.5 Stop)
Time: 2023-04-07 11:00 - 11:14 KST
Location: Dangjin, Korea
28 photos (14 each) processed with Pixelmator 3.3.2, RegiStax 6.1.0.8, and PIPP 2.5.9

This year's lunar eclipse was a long one, with the added bonus of having Uranus occulted by the Moon during the totality. This doesn't happen very often, and the next one is supposedly more than 200 years away. So I prepared my equipment and observed the progress at a good spot near home.

I did have some difficulties during the 4-hour session, as one camera battery couldn't last that long and dew was building up on the lens after 9 PM. But using a camera with a powerful zoom worked great for capturing the Uranus approaching and then hiding behind the Moon. It was literally a once-in-a-lifetime observation.

Device: Nikon P1000
Settings: 1500mm - f/6.3 (ISO 800 to 1600 / 1/3 to 1/250s)
Filters: None
Time: 2022-11-08 18:07 - 21:40 KST
Location: Naju, Korea

I visited Nangdo island in Yeosu about two hours before the second test launch of Nuri, a.k.a. KSLV-II. This place is about 17km away from the launchpad #2 at Naro Space Center in Goheung and is the closest place that you can watch the launch without any obstruction. The weather was extremely cooperative for photo and video shooting, so I was able to get some really nice photos. The following are some of the major shots I was able to get.