We often use a very useful website to keep track of when the International Space Station (ISS) will transit the Moon or Sun. The website is called ISS Transit Finder. Simply enter your location and it will tell you of ISS Lunar and Solar transits as well as near-transits (near misses) for where you are located and up to a certain “travelling distance”.
We were “alerted” to a pass of the ISS on the evening of March 30th just before 8pm, whilst it was still partly light, with the ISS transiting the Moon. The transit, which would be just before 19:58hrs and for the UK the visibility path stretched from Blackpool to Hull and would be only just over 5 mile wide. Furthermore, the whole transit event would only last ~0.7 seconds!
To capture this event a Celestron NexStar Evolution 6″ SCT and a DSLR was used. The telescope is easy and quick to set up and would easily track the Moon on the lead up and during the event. The field of view that the telescope/camera combination would give would allow the whole of the sunlit side of the Moon as well as some of the “dark side” to be captured to give a nice field of view for the ISS transit. As the event would last less than a second a high frame rate would be needed, and the DSLR in video mode would allow 60 frames per second but with an crop factor of 1.3x on the sensor. This still gave a nice field of view however.
The telescope was set up about 30 mins before hand to get everything in place and set up. Typically clouds intervened but initial alignment, exposure and focusing was done between the clouds using the camera’s live-view mode, with 10 minutes still to go before the transit. I had set an alarm on the mobile to give me a 2 minute warning which, when it sounded, the video sequence began recording. With a little telescope adjustment to get the Moon framed as I wanted it, the 30 second countdown began. It seemed like an eternity watching the live-view screen with intermittent clouds passing by. Had I missed the event. Had clouds obscured the ISS?
Just as the last “had I missed it” thought crossed my mind a bright “dot” quickly passed through the camera screen from middle right to top left. Blink and you would have missed it. It was the ISS. I big smile crossed my face. I had captured my first ISS Lunar transit! I stopped recording, packed up the equipment and went to the computer with the camera’s SD card in hand, loaded up the PC’s video software and looked at the frames. There it was! The ISS moving across the face of the Moon!.
The video below shows the ISS pass – and how quick it was.
Below is the same video as above but at slower speed.
I have still got some processing work to do on the raw video and images from it, but the initial results are below where you can make out the enormous Solar panels of the space station.
Next ISS Lunar transit I am looking forward to and I plan to “zoom in” closer for that pass!