Apr 3

ISS lunar transit – My best in this category!



This post is going to be one of my most memorable event in my ISS photography history yet! So here it comes..




My birthday was due on the 23rd of March, I turned 40 which alone is a big enough event for a day. I do not think anyone loves birthdays after a certain age… Anyway since the website Calsky went down, finding out solar/lunar transits became somewhat more difficult. These days I regularly check the transits in ISS Transit Prediction android app or Transit Finder website, they both are pretty good and most importantly accurate.

Soon I realised that a lunar transit will happen on my birthday! I took a day off for other reasons anyway, so I decided to grab my chance and go for the event – if the weather permits. I had a busy day, had to rent a car for a few hours but the weather forecast looked very promising! So I packed the car with my gear, made my way to Chiswick (London) where I had other stuff to do first. After sorting some things out I looked for a relatively quiet side street to do my setup. The photos above are from Heavens Above website (not the app). Once I knew what was about to happen, Heavens Above was a huge help too.
When the Moon is high in the sky – maybe at its highest it can be seen from London – it offers the best possible chance for a lunar transit. Higher the Moon is hanging in the sky, the closer the ISS is to my location. Similar to airplanes, closer to the horizon they are, smaller they appear to the observer. Close to zenith (right above the observer) they are, larger they appear. Moon was at almost 60° above the horizon and the ISS was ‘only’ 483km away from me.


Perfect opportunity!




With a couple of friends we decided a year ago to start the Spacejunkie youtube channel, where we broadcast live space related events and our space related programs. Since many of our hungarian viewers showed interest toward the ISS, I decided to broadcast it for them exclusively in my own native language (hungarian). This is a shortened version of the live broadcast focusing mainly on the event.


Love these lunar transits when the ISS is illuminated. Mainly because you can see the event with naked eye too. As my live broadcast shows, even my phone could pick up the bright dot that appeared from the westerly direction, approached the Moon and at the right time the actual transit happened. The fact that weather and atmospheric conditions were really really good, this was the perfect birthday gift!

Then I packed away, left the scene and dropped off the car and went home. The story did not end here, actually the misery only started but first let’s see how processing went on.




I had two similar projects in the past. First one recently happened when the ISS flew near Moon and the secon happened in February 2019 when a very similar event happened, namely the ISS transited our Moon. I followed the image processing method I successfully experimented with at the latter event.

First I did put together the frames as they were captured – post-processed, but no cropping involved. I love how cool Moon looks, no crazy distortion due poor weather, instead crisp images.

These frames can be layered on top of each other, so it will include all the ISS frames on one composite photo. Look it is an armada of space stations! My favourite bit about the composite photo is how the solar panel stands out or blends in, depending on what colour and brightness the background is. Worth opening the photo in large and to follow the ISS in front of the lunar surface.


But the real surprise always comes when the station is centered and cropped around on every frame (with the station on it). Suddenly the whole perspective changes and gives us a feeling that we fly side by side with the ISS whilst filming it passing in front of the southern lunar limb. I always apply this approach when possible. Sadly transits like this are pretty rare!



I am really happy about this observation, the best way to start my 40’s haha!



Skywatcher 250/1200 Flextube dobson telescope
Zwo ASI224MC camera
TMS-Astro Eq-platform

London, UK

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