Wesley's Tool-Box

The International Space Station was to make a very close pass to Rigel, one of the brightest stars making up the Orion constellation, last Saturday evening where I live. The separation at the closest point was around 0.055°, making it look like the space station passing right over the star to the naked eye. Instead of manual tracking, I decided to fix the telescope on Rigel and record the pass with iPhone X's 4K 60fps video mode. A total of 50 consecutive frames captured the rapid movement. The windy condition, coupled with relatively low angle (35.6°) blurred the results a lot, so I should try this technique again at a higher angle.


Here's the rotated video of the pass, once at the original speed and once at the slow speed.

Telescope: Celestron NexStar 6SE + X-Cel LX 9mm eyepiece
Device: iPhone X (afocal)
Settings: 28mm - ISO 880 - 1/1500s - f/1.8
Filters: None
Date/Time: 2018-03-24 20:00:59 KST
Location: Naju, Korea

When you try to keep up with fast-moving objects with the manual control of the telescope motors, the lack of fine-grained steps become a big limitation. Speed 6 moves at about 0.267 degrees/second and 7 at 1 degree/second, while the International Space Station moves at a speed that is somewhere in between, depending on the distance. To alleviate this slightly, practice and preparation were needed. I fixed the finder scope misalignment and added a camera mount to the telescope. iPhone 6 Plus was placed on the mount to act as a secondary finder scope, much like what I did on my Canon SX50 HS camera three years ago. These made it much easier to have the telescope point at the International Space Station.

As a result, I managed to photograph about 220 frames of the station in two minutes this time, enough to show the movement like the one I did with the old camera two years ago when I came to Naju. The space station was farther away and a lot dimmer (504km vs 685km, -3.5 mag vs -1.6 mag at culmination) than the previous attempt with the telescope, meaning less details. Even so, I think I was able to identify the SpaceX Dragon spacecraft that went up for the CRS-9 mission, which was attached to the bottom of the Harmony module just ten days before.

Telescope: Celestron NexStar 6SE + X-Cel LX 9mm eyepiece
Device: iPhone 6S Plus (afocal)
Settings: 29mm - ISO 720 - 1/1400s - f/2.2
Filters: None
Date: 2016-07-30 KST
Location: Naju, Korea
Stacked with PIPP 2.5.6 and RegiStax 6.1.0.8

Photos: 10 / 9 / 12 / 6 / 9 / 12 / 28 / 4 / 10 / 14 / 8
Time: 20:18:58 / 20:19:07 / 20:19:12 / 20:19:26 / 20:19:39 / 20:19:41 / 20:19:45 / 20:19:50 / 20:19:58 / 20:20:06 / 20:20:12

Directly imaging a fast-moving object in the sky like ISS by tracking it manually becomes more difficult with higher magnification. I could barely manage it with the Canon SX50 HS camera with 1.46"/pixel resolution. Using iPhone 6S Plus on the NexStar 6SE telescope with a 9mm eyepiece gives 0.31"/pixel resolution, making the field of view nearly 5 times narrower. Indirect method, which images the moment when the ISS passes in front of another celestial object, is easier because the telescope is focused on a fixed location. This is what I did a year ago. But such opportunity is much harder to come by, so I eventually decided to give the direct method a try with the telescope.

There were many uncertainties, such as what camera settings I should use on my iPhone and whether the telescope's motors would be fast enough. I would have to make guesses and hope for the best. To increase the chances of catching the moments at a high resolution when it entered the view, I used the 4K (3840x2160, 8.3MP) 30fps video recording mode with highest ISO and fastest shutter speed possible. One thing I did manage to "tie down" was the iPhone itself. The Universal Smart Phone Adapter from Modern Photonics that arrived in the mail just in time was the best solution I tried for attaching the phone to any eyepiece I had.

In the end, I was able to capture 22 frames in total out of about 100 seconds of recording. Targeting the space station with a non-magnified finder scope turned out to be quite difficult and focusing was also somewhat tricky. I need more practice to nail these down better. Fortunately, the motor was more than fast enough and the camera settings worked out. Plus, the processed results already outdid the ones from SX50 HS - major parts of the station are much more recognizable. They also explain what I was looking at in the old blurry shots. Looks like I'll be trying more of this in the future.

Telescope: Celestron NexStar 6SE + X-Cel LX 9mm eyepiece
Device: iPhone 6S Plus (afocal)
Settings: 29mm - ISO 720 - 1/1400s - f/2.2
Filters: None
Location: Naju, Korea (time in KST)
Stacked with PIPP 2.5.6 and RegiStax 6.1.0.8

#1: 9 photos @ 2016-06-17 20:39:38
#2: 5 photos @ 2016-06-17 20:40:03

It seems that I get to see a "great" transit of the ISS in front of the Sun once every year, with the space station appearing large enough to make it look like the letter H. This time, CalSky was predicting a nearly perfect condition at Naju, a near-center pass with an apparent diameter of more than one arc minute (63.1"). With the weather cooperating, I did not want to miss it.

To make sure I did not miss anything, I took out both my Celestron telescope with the smartphone adapter and my SX50 HS camera. I was hoping that at least one of them would catch the occurrence. I hurried with the setup and had everything ready just barely. I let my iPhone 6 Plus start recording the view through the eyepiece of the telescope in 240fps slow motion video, and pushed the shutter on my SX50 HS in continuous shoot mode, all mere moments before the transit.


The SX50 HS captured just one frame, which was sort of expected. The quality was easily better than my previous attempts thanks to the large apparent size. But the real deal was in the iPhone 6 Plus. It had captured 80 frames of the ISS in motion in total, with each frame besting the SX50 HS's efforts. The 240fps video capture truly shined, creating this smooth slow motion video as a result.


Here's the stacked and post-processed composite of the video in a single picture; click it to see it in full resolution. You can appreciate the details of the ISS and the sunspot AR 12339 quite better this way. If you look at the space station up close as seen in the first picture of this post, it's good enough to identify its major features. I've marked them for your convenience.

Telescope: Celestron NexStar 6SE + 25mm eyepiece + 2.5x barlow
Device: iPhone 6 Plus (afocal)
Settings: 29mm - 1280x720 - 240fps - f/2.2
Filters: None
Time: 2015-05-10 13:33:58 KST
Location: Naju, Korea
Stacked with RegiStax 6.1.0.8
- #1: 12 photos
- #2: 10 photos (ISS, each) / 100 photos (Sun)

Yesterday evening presented a rare opportunity of viewing the sun-lit ISS whizzing by the Moon from where I live. Luckily, the weather cooperated and the sky was mostly clear of clouds. I initially set up a telescope to see it, but the apartment window was too limited for it to calibrate in time, so I fell back to using my SX50 HS's zoom capability instead.

A few minutes before the crossing, the space station started to appear on the western sky. So I told my daughter Celine to come over and see the phenomenon together; we watched it gracefully travel eastward. When I saw that the ISS was about to transit the Moon, I let the burst mode of the camera snap 10 photos in rapid succession at 13fps. Then, we kept watching the ISS until it disappeared into the eastern sky.

Checking the photos, I noticed that the dot the ISS was supposed to be was smaller than what was expected according to CalSky, which predicted the transit. Then I looked at the first photo where the Moon got behind the ISS, which showed a "shadow" much longer than the dot. This is when I realized that the dot was the central area of the space station and the shadow was its solar panels. The size mystery was solved.

For those of you who would like to see a full resolution composite of the ISS-Moon transit, [click here] to load the image. It's a bit sad I can't adjust the ISO setting while shooting in burst mode with the camera - I would've like to have it lowered for less coarse images.

Device: Canon SX50 HS
Settings: 1200mm - ISO 800 - 1/1000s - f/6.5
Filters: None
Time: 2015-04-24 19:56:49 KST
Location: Naju, Korea

The roof of the new KPX headquarters at Bitgaram City in Naju is dubbed "Sky Park", so I thought it might be an interesting spot to photograph celestial objects. It is surrounded by small windows, obscuring low altitudes, but a good place otherwise. On the evening of the day after Christmas, a flyover of the International Space Station was expected on a clear sky, so I brought my Canon SX50 HS camera to the roof.

It was very windy and cold, and my bare hands holding the shutter button began to feel numb almost immediately. Luckily, the ISS began to appear on the western sky, so I pointed the camera towards it, helped by the iPhone 6 Plus mounted on the hot-shoe. In the span of about 3 minutes, I was able to take roughly 400 photos of the space station, of which 40% was in good state.

The 25 best shots can be seen here, starting at 18:37:00 and ending at 18:39:44, at about 7-second intervals. During most of the visible flyover time, ISS was turned on its "back", and then "rotated around" around 18:39:00, only to disappear about a minute after. The turnaround point was when it was closest to the observer, about 560km away. The animated version with each frame 5 seconds apart should illustrate this quite nicely.

What I like about this observation is that the ISS was captured on camera more clearly than most of the attempts made in Suwon, except for the direct overhead pass last year. The morning flyover photographed last March shows the opposite turnaround, but was much blurrier. The difference is quite noticeable. Looks like I'll be able to enjoy doing astrophotography even more at this new location.

Device: Canon SX50 HS
Settings: 1200mm (2x enlarged) - ISO 80 - 1/320s - f/6.5
Filters: None
Time: 2014-12-26 18:37 - 18:40 KST
Location: Naju, Korea

This series of images I took of the International Space Station (ISS) seem to explain the "sideways" view of the station I've taken a few times before better. Until the close approach, only the center area is visibly illuminated. At the closest point, the solar panels stretching from top to bottom become apparent.

The panels form the two columns of the "H" shape when viewed from the "front". But in these images, the shape is more like a mirrored "ㅔ". I guess this view can reveal a docking spaceship, if there is one and is big enough.

Device: Canon SX50 HS
Settings: 1200mm (2x enlarged) - ISO 160 - 1/320s - f/6.5
Filters: None
Time: 2014-04-06 20:35 KST
Location: Suwon, Korea
Max Magnitude: -3.6