SDO lunar transit: now with video!

By Phil Plait | October 20, 2010 8:46 am

Yesterday I posted a beautiful image of the Moon transiting the Sun’s disk as seen from the Solar Dynamics Observatory. Well, today NASA put up HD video of the event!

[It may take a minute to load, it’s a big file.]

Wow! You can see the Sun’s rotation over the four hour interval these pictures were taken, and then the Moon flashes by. The Moon is dark because it’s between us and the Sun, so were seeing the unlit side (I have a diagram showing an approximation of the geometry of this event on my other page about it).

Moreover, scientists can use images of the sharp-edged Moon against the Sun’s disk to check on the optics of the observatory. That information can be used to sharpen the images even more. So this is fantastic, fantastically beautiful, and fantastically useful, too.

Tip o’ the sunglasses to NASAGoddard.


Comments (15)

Links to this Post

  1. Un eclipse parcial desde el espacio « [Px] | October 20, 2010
  1. Heather

    Is there any particular reason why the path of the moon seems to be curving? It starts low on the right, then goes up, then seems to be going back down when it’s completing the transit.

    Or is that just the way the video was recorded?

  2. Messier Tidy Upper

    Wow. Awesome clip. 8)

    The Moon moves so fast! :-)

    @ 1. Heather : Well spotted. I see what you mean but I don’t know why that is. My guess – and it is just a guess – perhaps its the Solar Dynamics Observatory moving as it tracks it? Or possibly an optical illusion of some kind .. Or .. no, surely not lunar libration at work!

  3. Gary Ansorge

    Illusion. Curved surfaces passing across one another can have that effect.

    Gary 7

  4. Heather

    @Gary Ansorge


  5. Jeff


    I’m living to see astronomy like a sports event with real time video and all. Amazing.

    I remember in about grade school they said planets around other stars wouldn’t ever be discovered. We’ve come a long way baby.

  6. We like da moon….coz it is close toooo us…..

  7. P_Buttah

    I really enjoy the “loading” sequence animation of the video.

    A blue dot and punk dot transiting eachother, before a video of a gold dot is transited by a black dot.

  8. @Gary I thought that too at first, but then I looked closely and the apparent curvature seems to be present. My guess is that it’s due to some ponzo (perspective) illusion.

  9. Messier Tidy Upper

    @4. Heather Says:

    @Gary Ansorge – Thanks!

    Seconded by me. :-)

    @8.scibuff : Thanks also. Wow! That was quick & great work. Well done. :-)

  10. @ Heather, Gary, et al:

    Could the curved path be due to the fact that the orbit of the spacecraft is inclined somewhat to the plane of the moon’s orbit around the earth? That would give you the appearance of a curved path as the moon transited in front of the much more distant sun.

  11. Heather


    So perhaps this came during a “dip” in the orbit of the SDO where it appears as if the moon goes up a little bit? Or that the alignment of the orbits isn’t all on the same plane and the video happened long enough to capture that fact?


    That was a really cool trick with the video.

  12. Chrispy

    “The Moon is dark because it‚Äôs between us and the Sun, so were seeing the unlit side”

    Yes but, exposing for the sun, wouldn’t the moon appear dark even if we could see the lit side at the same time? Or maybe the ‘dynamic range’ of this instrument would be great enough to capture both? Or maybe I am not understanding something here ūüėČ

    Sorry if this was already addressed in the previous thread!

  13. @ Heather:

    Essentially, yes. The spacecraft could be below (or above) the plane of the moon’s orbit, thus it would see the moon travel along a slight arc, rather than a straight line as it would if the spacecraft were in the same plane as the moon.

    Mind you, I’m just guessing that is the correct answer, but it seems the basic geometry of the orbits is at the heart of the apparent motion. Either that or…


  14. Messier Tidy Upper

    @ ^ : On DVD? ūüėČ


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