When natural and artificial moons align

By Phil Plait | December 30, 2010 7:00 am

A few hours before last week’s lunar eclipse started here in the States, the phenomenal astrophotographer (and frequent BA Blog photo contributor) Thierry Legault was in Normandy, France, and got a magnificent picture of a different sort of transit involving the Moon:

Wow. You definitely need to click to enlunanate and get the giant version. The full Moon would be enough to make this a nice picture, but look more carefully, just above the bright rayed crater Tycho. See that weird silhouette?

That’s the International Space Station! Thierry used software called CalSky to determine the exact time the ISS would pass in front of (transit) the Moon, and was able to snap this shot during the 0.55 seconds it took the artificial satellite to pass in front of the natural one. At the time, the station was 420 km (250 miles) away, yet the detail in the shot is astonishing. You can clearly make out the solar panels and trusses of the station.

Hmmm. Come to think of it, the Moon is about 380,000 km away, so it’s roughly 900 times more distant than the space station in this picture. However, it’s also 35,000 times bigger, so even its much greater distance doesn’t diminish its dominance in this photo. It’s a stark reminder that we’ve explored very little of the millions of square kilometers of lunar surface.

Also on his page, Thierry has a couple of gorgeous lunar eclipse images well worth your time to look at. In fact, just go to his site and poke around. Thank me later — much later, because you’ll be there a while.

Related posts:

ISS, Shuttle transit the Sun
Two solar ISS transits
AMAZING Shuttle picture
EXTREMELY cool 3D Space Station video taken from the ground
Check. This. Out. Amazing photo of the Sun…

CATEGORIZED UNDER: Cool stuff, Pretty pictures
MORE ABOUT: ISS, Moon, Thierry Legault

Comments (69)

  1. Jason

    That is a very cool picture. It helps drive home a sense of scale

  2. Great picture. It must be fun getting all that cool stuff from readers. :) But I will say I’m glad they send it to you because to showcase this stuff well.

  3. AtomicTommy

    That’s just plain awesome…wallpaper time! :)

  4. Gary Ansorge

    What I want to know is, how did he get such a detailed image of the space station against the lunar back ground w/o the lunar illumination swamping the photo?

    Now, THAT’S wizardry.

    Gary 7

  5. Messier Tidy Upper

    @4. ^ Gary Ansorge : Indeed. Me too. :-)

    Wow. Magnificent photo. Superb work by Thierry Legault once again. :-)

    Imagines the International Space Station was *really* orbiting the moon. Acting as an interplanetary (Interlunar? Selene-drical?) exploration spacecraft rather than just being in Low Earth Orbit. Sighs.

    PS. Thanks, BA, for reminding us all in your chosen title that the word “satellite” also applies to the natural as well as the artificial bodies. :-)

  6. That’s no m…oh, I just can’t.

  7. Uite

    What I really like about this picture is how you can see that the moon isn’t exactly round; it’s full of bumps and dimples!

  8. For some reason I have The Blue Danube waltz running through my head.

  9. Fizzics Teacher

    Wow, another photo to use as wallpaper. I want a job like Thierry Legault ; perhaps he needs a flunky to carry the camera cases and tripods?

  10. Martha

    @ #6 That’s no moon that’s actually Nibiru!

    (you can’t make this stuff up: http://www.godlikeproductions.com/forum1/message551816/pg1

  11. This is, without a doubt, one of the coolest photos I’ve seen this year.

    It really makes you think what things will look like when or if anyone ever builds a a space station ala “2001: A Space Odyssey” at a lagrange point or something.

  12. This is a good addendum to your post the other day debunking the supposed space ships traveling to Earth to destroy the human race in 2012.

    This is a great demonstration of the scales involved.

  13. MaDeR

    “Imagines the International Space Station was *really* orbiting the moon.”
    No. Not this crap again. It cannot be done. ISS is not built to work, operate and survive in this environment. Ther is no possibility and no sense in moving ISS to orbit around Moon. Just… stop…

  14. This is SICK! Legault has clearly sold his soul to the devil to get these shots.

    (Where do I sign up?)

  15. Ah, my new desktop background. THAT. IS. AWESOME.

  16. Crux Australis

    MaDeR: relax. It’s a nice fantasy.

  17. Yeah, Messier Tidy Upper. Please stop imagining things that aren’t presently feasible.

  18. Craig

    M-O-O-N. That spells International Space Station.

  19. the transit time was a little over half a second? (0.55 seconds) or 55 seconds. sorry dense today. well i am in texas after all. ;-D

    if it’s the first, WOW whata catch!!!

    Awesome pic no matter what.

  20. Keith Bowden

    [Bad Bunny! lol (#6)]

    That’s not the ISS – it’s replicating monoliths! (C’mon, it’s right over Tycho!)

    [edit – Thank you, Phil!]

  21. scgvlmike

    I just had a thought (it happens from time to time): I know one of the astronauts who is either on the ISS (I still think of the station as Alpha, because that’s what the first crew called her) or was up there recently enjoyed taking photographs of the Earth’s surface from that vantage. If that camera were pointing at Normandy as Legault was taking his picture, would that not be a perfect example of the Nietzschean quote, “If you stare into the Abyss long enough the Abyss stares back at you”?

  22. KSE

    My first thought when I saw the pic (unmagnified) was of a TIE Fighter… I can’t be the only one right?

  23. I want to be on the ISS.

  24. gruebait


    I decided that must be the camera exposure time.
    Roughly 90 minutes per orbit.
    Roughly 1/4 minute (time) to cover 1 degree (arc)
    So, something like 7 seconds to pass across the moon’s disk.
    At least, that’s what is on the back of my imaginary envelope.

  25. Levi in NY

    I’m actually surprised the ISS is 1/35,000th the size of the Moon’s diameter. I’d have thought the Moon was bigger than that. Then again, the human brain was never designed (figuratively, non-creationistically speaking) to conceptualize such enormous sizes.

  26. Monkey

    Re: how did he get the image without moon-saturation

    ..perhaps two image overlay? One of moon focus, one of ISS focus, overlay and both ceom out perfectly in focus? Just thinking….probably wrong.

  27. Monkey

    @ scgvlmike Says:


    Or, who watches the watcher….

  28. Joel

    Absolutely stunning picture. I am in awe of the amount of detail on the moon itself, let alone the awesomeness of the transiting ISS.

    Question for everyone: What’s the peculiar bright white spot at about nine o’clock on the moon’s disk here? I’m guessing it’s just a peculiar crater (well, I’m hoping it’s not a Cyberman advance base for an upcoming invasion, anyway), but why is it so bright?

  29. JB of Brisbane

    The Naked Bunny beat me to it this time…

  30. Richard Woods

    “What’s the peculiar bright white spot at about nine o’clock on the moon’s disk here?”

    Aristarchus Crater

    “why is it so bright?”

    The impact that created it was more recent than almost any other major lunar feature’s origin (except Tycho). Aristarchus’s exposed material hasn’t had as much time to be darkened by the solar wind as most other lunar surface.

  31. Monkey

    Re: Joel
    That bright spot is Hoaglands secret base on the moon…

    …or perhaps a coincidental alignment giving reflection of a crater a nice bright appearance?

  32. I don’t have the math skills to do the calculations, but that 0.55 second IS the length of the pass of the ISS in front of the moon. I’ve watched it cross the sky, and it moves!

    I’m sure M. Legault timed his shot perfectly; in fact, he may well have taken a burst of shots. The 5D can take 3.9 frames per second. As far as getting the exposure to correctly expose both the moon and the silhouette of the ISS, he just shot for the moon. The ISS is just an unlit black shape in front of it.

    I want to do this! With CalSky, a great telescope, a great camera to attach to it, and a lot of practice, it could be done. In fact, this would be much easier than his amazing video captures of the ISS as it whips across the sky. If you know the ISS is going to cross in front of the moon at an exact time in a given place, then you just get to that place, aim you scope and camera at the relatively still moon, focus, take some preview shots to get the exposure right, and shoot a burst at the right time. The final shot will be great just as long as you catch the ISS in front of the big old (half a degree wide) moon (and, of course, have great seeing and a sturdy mount). For the video, you’d have to get the fast-moving ISS into the very center of your field of view, lock on it, and record the tiny shape on the tiny sensor in your planetary camera.

    The newest DSLRs have such great noise reduction that you can use ISOs as high as 1600, so exposure times can be very short, freezing the moment so that bad seeing doesn’t blur the shot. I have a Canon 500D coming in the mail, and several fairly decent scopes. I think I’ll give this a try. I’ll just keep my expectations low.

    I envy him his equipment, his patience, and his amazing skill!

  33. Wait, maybe I do have the math skills to make a guesstimate. When it crosses the entire sky (180 degrees) at a given location, the ISS takes about five minutes, or 300 seconds. The moon is about 1/2 degrees across, so, 1/360 the distance across the sky. 300/360 = .83 seconds, which is pretty close to .55. The angle was no doubt less than straight across the sky, and/or the ISS didn’t cross the entire face of the moon.

    Sorry for the pedantry! Maybe I’m way off here, anyway.

  34. Mchl

    @Gary #4, @MTU #5: The Moon in the picture is full (or pretty close anyway), which means both the station and the Moon are lit equally well. The Sun is behind the photographer. That’s why the brightness of the moon does not dominate (well, not by much) the picture.

    It als helps that ISS’s solar panels are always directed towards sun, which means it was probably as bright as it gets when the picture was taken.

    @Monkey #28: for all practical purposes the Moon and the Station are both in ‘infinity’ range, which means they both can be pictured with same focus setting.

  35. Messier Tidy Upper

    @ ^ Mchl : Thanks. :-)

    @17.Crux Australis : MaDeR: relax. It’s a nice fantasy.

    Exactly. Thanks. :-)

    Yes, MaDeR (#14) I know they can’t do it & no, it wasn’t a serious proposal just me wishing and imagining we were living in a better world where we’d gone – & were keeping on going – so much further and higher and better than we have done in this reality. It’s called imagination MaDeR, try it sometime.

    @6. Naked Bunny with a Whip : That’s no m…oh, I just can’t.

    LOL. Kudos for trying anyhow! 😉

  36. Messier Tidy Upper

    @9. kuhnigget : For some reason I have The Blue Danube waltz running through my head.

    You mean like this? :


    Now *that* was a space station! 😉

    That was also supposed to be built and operational back in 2001 .. Ten years ago now. Yikes.

    @ Everybody here :


    Hope y’all have a great 2011.

    (Btw. It’s just over half an hour from the New Year here in Oz.) :-)

  37. Eric Juve

    That is an awesome shot and thanks for the link to CalSky. I had never known about it before. BTW if you donate it works even better.

  38. Joel

    Thanks guys. I feel educated now. It’s certainly a striking feature, I’ll have to try and get a proper look at it one of these days.

  39. Messier Tidy Upper

    Off-topic, sorry, but thought this may be of interest to the BA & other folks here :


    Birth of a new year, galactic birth structure of new super-bright stars, sounds apt! :-)

    Guess the BA (& many others) may already have heard of & seen this but just to make sure.

    PS. Midday 1st Jan 2011 already here in Oz.

  40. Chris

    Spend all that time trying to get a nice moon shot, and the space station has to fly right over it!

  41. magetoo

    “The Moon in the picture is full (or pretty close anyway), which means both the station and the Moon are lit equally well. The Sun is behind the photographer. That’s why the brightness of the moon does not dominate (well, not by much) the picture.”

    Don’t forget that there’s also a giant freaking planet involved (behind the photographer, that too). And this would have been, what, maybe two hours away from midnight?

  42. Good effort. I love photos like this.

  43. Markle

    #37 Mchl Unless shot right around sunset/moonrise (shot from France before totality) the ISS would have been in the umbral shadow. A 1/2 degree cone with 6370km radius covers a lot at 400km altitude. Graphic depicting size of umbral cone with Earth and moon to scale. I’m not inlining that because it’s really too big for the forum layout.

    P.S. Since when have proper a tags been getting sent to moderation? It used to be only bare links went to purgatory

  44. Sad to say I missed the eclipse here in Cairns because of heavey clould cover and rain. This photo is truly awe-inspiring!

  45. un malpaso

    I love these pictures of spacecraft transiting celestial bodies. Besides the fact that they are beautiful, they inspire me in that they combine the awesomeness of space with the astonishing reminder that we are still putting things in it of our own creation, and that we coexist in a spectacular universe. Seeing them both in the same picture is also a powerful reminder that, despite our baby steps and steps backwards, we humans are still in space, man! That we are part of the universe too, and that we ill hopefully be exploring it for a long time to come.

  46. jennyxyzzy

    OK, maybe I’m doing something wrong, but playing around with CalSky, it doesn’t seem that that ISS/moon transits are visible from northern France – can someone that knows a bit more about astronomy confirm that?

  47. Lisa

    Every month is the library, we host a different “theme”, including fiction and non-fiction.

    This month is science! The head librarian was focusing on physics, but I argued to have astronomy included. My “Phil never actually posted any of those Vegas pictures” surely helped.

    I talked to many students today, and they’re excited about science month. The photo on this post is already making the rounds.

  48. Vinix

    About the problem of moon light saturating the image.
    Well, it actually saturates!
    Thus the ISS is totally dark in this picture, but you can see details just because the background is so clear.
    About focus: probably 420 km and 380.000 km are not so different, from a scope focus point of view.
    On a standard camera they would both be “infinite”, definitely.

  49. Vinix

    @36 Actually, an ISS pass lasts about 9 minutes, even almost 10, on a given location and this doubles your estimates, but of course the moon “occultation” can last much less.
    Let’s say that a pass of this kind can last no more than about 1.7 seconds in the most favorable case.

    Please go to http://www.amsat.org, section ‘passes’ to calculate times of passes above your location.
    When this happens you can normally do two things: listen to 143.625 and 145.800 MHz FM, listening fro some activities and, if the pass is justbefore dawn or little after sunset, SEE the ISS with the naked eyes, as a bright star passing by. I bet you will impress your friends!

  50. useitorlose

    How did that tie fighter get way out here all on it’s own? And why is it headed toward that moon? Wait a second, that’s no moon …

  51. Obi von idO

    Really cool photo!

    But why do the Death Star have a lot of big craters on it?

  52. savannah

    Really cool!!!!!!!!!!!!!!!!!!!!!!!!!!:'( (^^^) <3 :)


Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!


See More

Collapse bottom bar