Capturing a pass of the X-37B OTV-5, and imaging an ISS transit over the Sun

click to enlarge

Yesterday evening was very clear, and the moon low in the south no real hindrance. I observed a very fine pass of the X-37B secret space plane OTV-5. It was an easy naked eye object. The photograph above (10-second exposure with an EF 2.0/35 mm lens) shows it ascending in the southwest, through Bootes (Arcturus is just above the open window).

The next morning (26 June) at 10:17:21 local time (8:17:21 UT), the International Space Station ISS was predicted to make a transit over the solar disc as seen from my house in Leiden.

I set up the Celestron C6 telescope in the courtyard, put a Baader Solar Foil filter in front of it, and hooked up the Canon EOS 60D to the prime focus. Instead of photographing at rapid burst, the technique I used for imaging with previous transits, I this time put the camera in HD movie mode. While this yields a lower resolution image than photography, the upside is that it yields more images showing the ISS silhouetted in front of the sun. And the ISS is big enough that the reduced resolution is not a real problem, the solar panels of the ISS are still well visible.

The image below is a composite of 21 frames from the resulting movie:

click to enlarge

Here is the movie itself, showing you how rapid such an ISS transit over the sun is (the total duration was only 0.8 seconds - it is over in a blink of the eye). The ISS had an apparent size of 45.8" during the transit, with the sun at 41 degrees elevation in the east:

The movie was made in the prime focus of a Celestron C6 (15-cm, F1500 mm Schmidt-Cassegrain, equiped with a Baader Foil solar filter) with a Canon EOS 60D DSLR in HD movie mode at 25 frames/second, with each frame having an exposure time of 1/4000th of  a second to avoid blurring the ISS. The track and time of the transit had been checked before the observation by loading the latest orbital elements for the ISS into Guide.

The biggest challenge with this kind of imagery is always to focus properly, certainly when the sun is spotless as it was this day. I always find focussing on the sun cumbersome. The focus this time turned out to be reasonably good though.

Yet another ISS transit over the Sun

Today, only a week after the transit of May 1st, I had another transit over the Sun of the International Space Station ISS here at Leiden. It happened on May 8, 2015 at 10:48:25 UT (12:48:25 local time).

The animated GIF above was made from four images and shows the ISS and clouds moving in front of the sun. In reality, the transit happens much faster than the GIF suggests by the way:it took less than 0.6 seconds in real time.

At first it looked like I would completely miss the transit: an hour before the transit it was still completely clouded.

About 20 minutes before the transit the cloud cover however started to break, and the Sun started to glimpse through. I quickly set up the Celestron C6  (a 15-cm Schmidt-Cassegrain) and while clouds were still partly obliterating the solar disc, I managed to snap a series of four images showing the ISS silhoueted against the solar disc. Unlike a week ago, this time a nice group of sunspots was visible as well.

Below are a still image and a detail from that still, showing the ISS with well recognizable solar panels just south of the sunspot group (note that the time in these images is 10 seconds off, it should be 10:48:25 UT).

click images to enlarge

Another ISS solar transit

On May 1st 2015 near 13:53:18 UT, there was another solar transit of the International Space Station ISS as seen from Leiden.

The weather was clear (apart from some thin cirrus) and I imaged the transit in the prime focus (F/10) of my Celestron C6, using the Canon EOS 60D at rapid burst (5.6 photographs per second). The telescope was equiped with a Baader foil solar filter and images were taken at 1/4000th second exposure (to avoid motion blur) and ISO 800.

The transit took place near the upper northern limb of the sun and was hence short. Only three images show it.

The image above is a stack of all three, superimposed on the first image. The image below is an animated GIF of all three images. In reality, the transit was much faster (about 0.4 seconds in total) than the GIF shows.

ISS transiting the Sun

click image to enlarge

Yesterday (June 23, 2014) near 16:15:29 UT (18:15:29 CEST), the International Space Station (ISS) passed in front of the solar disc as seen from my observing location in downtown Leiden. As can be seen in the picture above, the transit was nearly central (the calculated central line was 600 meter to the north of me). The whole event had a duration of about 1.5 seconds, during which 9 photographs captured the Space Station silhoueted against the sun. The images were made with my Canon EOS 60D through my Celestron C6 (15 cm Schmidt-Cassegrain), fitted with a Solar Screen filter and an F/6.3 focal reducer. The sun was low in the sky at an elevation of 31.8 degrees due West. The inset is a stack of the 5 best ISS silhouets.

The images are not perfectly sharp, which is due to air turbulence (even at 1/4000 second) and the simple fact that I find it quite hard to focus the telescope properly on the sun, certainly when it is almost featureless. Nevertheless, I am satisfied with this image.

I knew of the transit because I subscribe to alerts from CalSky for this kind of phenomena. In preparation for the actual observation, I download the latest ISS elements from Space-Track a few hours before the event, and load them into Guide to fine-tune the transit time and the path over the solar (or lunar) disc. Starting about 1 second before the calculated commencement of the transit, I start a rapid burst series of images at 5.7 images/second.

click images to enlarge

Above are two pictures of the setup used. The filter mount is homebrew and quite simple (from thin cartboard). The filter itself is Solar Screen, a mylar filter with a double thin aluminium filter coating. Using such a filter makes it safe to look at the sun (NEVER look at the sun without a proper filter!).

In order to be able to see anything on the camera LCD screen in the bright sunlight, I put a towel over my head and the telescope back during focussing.

ISS over the Sun

Late this afternoon (10 May 2011), at 17:29:25 CEST (15:29:25 UTC), the International Space Station (ISS) passed in front of the Sun disc again as seen from the SatTrackCam station, silhoueting the Space Station on the solar disc.

Like on March 24th, I used my small ETX-70 telescope equiped with a Solar Screen Filter, to photograph the event. This time I used prime focus plus a Kenko 2x converter, instead of eyepiece-projection, effectively yielding a f=700mm F/10 system.

Four images out of the series show the ISS silhouted againts the sun, along with several sunspots. Below is a composite image of the four images (showing the ISS four times), plus a detail. The ISS solar arrays are well visible.

click images to enlarge

The International Space Station (ISS) crossing the sun

The International Space Station (ISS) crossed in front of the sun disc as seen from my observatory this afternoon (24 March 2011) at 11:00:16 UTC (12:00:16 CET).

I used my modest 7-cm refractor (Meade ETX-70) to capture it: I started a series of rapid images (My EOS 450D takes 3.6 images/second) one second before the predicted pass time continuing for 5 seconds, and two out of this series show the ISS silhoueted againts the sun, with solar panels recognizable. The images also show a group of sunspots.

Below images are a single shot (with detail of the ISS at full pixel level), and an image which is a combination of the two images showing the ISS (hence the ISS silhouet shows up twice).

click images to enlarge

The telescope was equipped with a Solar Screen filter, exposure time was 1/500s at 400 ISO, eyepiece projection with a 26mm eyepiece to get a decent sized sun image (with f=350mm in the primary focus the sun disc stays a triffle too small).

Note that the telescope involved (see image below: Meade ETX-70 telescope with Canon EOS DSLR camera attached and solar filter on the lens) really is very modest: I bought it for a mere €200,- at the Lidl supermarket! The camera is 3 times as expensive as the telescope. Yet, this simple setup manages to capture it all, even though the images are perhaps not as sharp as you would like (which at least partly is due to air turbulence in the sun-heated telescope tube, by the way).