Feb 11

ISS – extremely good lunar transit

Lunar transit is something I’ve been craving for a long time now. I had some experience in this from the past, but it never turned out to be as good as I expected. But let’s be honest, it is not an easy task. Not only commitment required, but also circumstances must be perfect – Moon high in the sky, appropriate ISS pass, good light conditions, good weather conditions, etc.
I check Calsky every now and then just to know if something is happening. This prediction came up. Then double checked in Heavens Above.

I was not really sure what kind of composition should I go (if clouds clear). With illuminated lunar transits there are a few things one should pay attention. First of all if ISS passing in front of Moon, the station will blend into the background (lunar surface). Also the panels are rarely facing toward us (it always does toward Sun), mostly we see them from the side. Keeping these in mind I was planning to have ISS a little bit in front of Moon and off the lunar surface too. It seemed like a good combination, a bit of this and a bit of that… But the app I am also using (ISS Detector) is not always accurate though. If it had been a planetary transit, I would have been more worried, but with Moon a tiny error does not make any difference…
Life is the best director – I could not have found any better place for imaging, it all happened according to my expectations.

Because this transit happened during daytime, I assumed Moon and ISS will be much more pale. But after setting up the scope it was clear to me that the light conditions were just perfect. Moon was really contrasty on my laptop screen which gave me hope for something really good to come.
Below on the equipment photos you can see my dobsonian telescope on an eq platform. It usually tracks the sky well, but lately not that well, presumably gears are wearing off (need to be fixed). But I realised if I apply some pressure on the platform, it tracks very accurately. I placed my accessory box (a wine box basically) and the car jack as extra weight onto the dobson base – couldn’t find large enough rock in the carpark. (laptop is on a plastic sheet, not on the wet ground 🙂 )

I’ve tried to add all the frames with ISS on them and blend into on single photo. I did it but the final result is not something I really like to be honest. Daytime passes are trouble from this point of view, plus the seeing was not great- Whatever I did the lunar surface remained blurry. I’ll share the composite photo anyway…

Eventually a video I have made from the footages. Most importantly you will see the raw unprocessed footage of the transit at real time speed (double click on video for full screen).

Skywatcher 250/1200 Flextube dobson telescope
Zwo ASI224MC camera


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BoingBoing, Russia Today, CNET, RTÉDR

Hungarian (magyar)

24.hu, NLCafé, Időkép, HVG, Magyar Csillagászati Egyesület



  1. Andres


  2. Szabolcs Nagy

    Thank you both Andres and Partick for visiting my website and leaving your comments! ????????

  3. Gabor

    That is HUGE. Amazing!

  4. Szabolcs Nagy

    thanks very much Gabor! (köszi) 🙂

  5. Blake Cooper

    Great job that’s amazing!

  6. Kamil Keski

    Wonderful capture! Well done!!

  7. Angelo Meneghini

    Bellissimo, grande, davvero bravissimo!!!

  8. Szabolcs Nagy

    Warrwick Hoad that sounds awesome to read, down at the beach stargazing, I just love the idea! I sincerely hope you’ll get lucky with a transit.
    You can you my materials (with appropriate cradits), not problem at all! 😉

  9. Szabolcs Nagy

    Angelo Meneghini grazie mille!

  10. Elizabeth Williams

    WOW…loved watching. You did a great thing…thank you!

  11. Szabolcs Nagy

    Thanks Elizabeth! I’ve been waiting for a good opportunity since a while 🙂

  12. Szabolcs Nagy

    Tom Petraglia I love it, thank you! 🙂

  13. Chris Andreae

    That is surely a flying saucer with its nav lights on. The space station has a different profile.

  14. Szabolcs Nagy

    Chris Andrea
    Or it is ISS through turbulent atmosphere at daytime?! 🙂

  15. Nominus

    Chris Andrea
    Yeah, and it just happened to fly by exactly where the space station was supposed to fly in the exact same direction it was supposed to be flying at the exact time it was supposed to.

  16. Szabolcs Nagy

    Chris Andrea yes, that’s the beauty of mathematics! Most of the times ISS misses celestial objects like planets, Moon and Sun, but every now and then it all happens 🙂 Since they know the velocity of ISS and accurate altitude, they can calculate its flyby times (when it will cross the sky) and its elevation (in which constellations ISS will fly across in the night sky). And since we know the exact elevation of all the other objects in the sky (including Moon) at any given time and also the apparent size of every object in the sky (including Moon) it can be calculated, where you need to be exactly to see ISS crossing Moon right in the middle. When I use ISS Transit Prediction android app to check where the centreline is on the map, it also shows me the edges too. Edge here means when ISS appears very near to the edge of Moon, just like in my case. I knew precisely where I had to be to catch that.
    What we astrophotographers do when imaging planetary, lunar or solar transits is positioning ourselves according to accurate mathematical predictions, fr instance on Calsky.com website. And guess what, every singe time I followed these predictions it happened and ISS appeared exactly where it was supposed to.
    But the most beautiful thing is that you can try it and test it yourself at almost anytime. Just check the websites or apps I mentioned in my webpost, get a pair of binos (ideally a telescope) and see it for yourself. After that if you still wont’t believe it’s there and it’s real even when you saw it, well…. I don’t know what to say then.

  17. Chris Andreae

    You make it sound so easy! Still, it is encouraging that the ISS ‘misses’ the Moon and other celestial objects most of the time. There are enough craters there already.

    I must wind up my own telescope – I probably need to get a new one as the present one does not work very well – and see if I can spot more than a few stars in the light-polluted sky of south of England (my bit anyway). I have a rather smart new camera that is champing at the bit, too.

    Thanking you for the advice/comment.


  18. Gary

    Very nice work I have a transit coming up this Sunday.

    Did you use a barlow or is this prime focus and full resolution 1304*976 ?

    I have imaged it before by chasing it using a 0.8ms shutter speed can I ask what speed you used for this shot?

    thanks, Gary

  19. Szabolcs Nagy

    Hey Gary!

    I did not use any barlow lens and used camera at full resolution.
    I can’t recall now the exact shutter speed, but I always set the value (and gain as well) according to circumstances. But always try to keep shutter speed as low as possible, not at any cost but I wouldn’t go over 1ms, otherwise ISS gets blurred.

    I only use fix values for shutter/gain when imaging ISS flybys, otherwise always improvising 🙂

    Best of luck to your transit and please let me know how it went. Also I have a guest gallery in this website, in case if you have any good shots from the past or this coming up event turns out to be successful 😉


  20. Amanda Kooser

    Hi Szabolcs, I’m a writer with CNET and I’d love to cover your lunar transit imagery in an article. Is there a good way to get in touch with you? Would Facebook messaging be best? Thank you! Amanda

  21. Szabolcs Nagy

    Hi Amanda,
    I will get in touch with you soon and we’ll talk about how is the best way to communicate.

  22. M J

    Stellar results.
    Your ‘weighty’ problem-solving solution is so very grounding,.
    Most importantly, it humbly brings us back to earth.
    Love it!

    Thank you so much for sharing.

  23. Szabolcs Nagy

    Thanks for your comment, much appreciated! The weight solution was an unintentional discovery 🙂 Since that afternoon I had an imaging session on Moon and when I did put some weight on the motor side (this time around with normal circular shaped weight for weightlifting) and the eq platform performed superbly good 😉 Everyday is an opportunity to learn something new!

  24. Peter beckles

    men i in never seen anything that fast in my life woohoo

  25. Szabolcs Nagy

    ISS is quick just by looking at it during a morning/evening flybys, but it looks quicker when passing by a fix object in the sky. Crossing the disk of Moon is somewhere between 0.5-2s depending of how far ISS is from the observer’s location.

  26. Peter Vogel

    Outstanding and inspirational.

  27. Linda K Meherg

    Thanks I never would have thought or seen it thanks keep it ???????? coming.

  28. Szabolcs Nagy

    Peter Vogel
    Awesome, thank you! ????

  29. Szabolcs Nagy

    Linda K Meherg
    Thank you, will do my best. I only need good weather ????

  30. Ivo

    Amazing video!!! I had no idea you could get such a detailed view of the ISS? Wondering: are there any sattelites you could photograph like you did with so much detail? Or are they too small and too high up?

  31. Szabolcs Nagy

    Hi Ivo,
    Thanks for visiting my webpost! Yes ISS is a very “photographable” object (more photos in my Gallery). Smaller objects can be photographed too, but it becomes really hard due their distance and apparent size.
    Satellites, rocket first and second stages are visible, also cargo spacecrafts too when they are heading to or from ISS. I personally managed to take a shot of all of them, which counts to me as the most difficult task of all. They are very faint and was very hard the correct exposure settings.

  32. aranyosfodorka

    Csodálatos képek. Látom néha az ISS-t, de olyan messze van !
    Köszönet, hogy „közelebb hoztad”!

  33. Szabolcs Nagy

    Nagyon szívesen, próbálkozom én elég sokszor, csak az a fránya időjárás… 🙂

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