Wednesday, April 16, 2014

Lunar Eclipse, April 14 - 15, 2014

Photos - Observations - And don't miss the video at the end!

I took pictures of the moon about every 15 minutes during this last eclipse (except when it got too cloudy!)  :(    Here is a time-lapse montage of how the moon changed shape and brightness during that time. 

Time lapse of 2014 lunar eclipse

"Emergence from Eclipse" Video

This is a really interesting exercise in observational astronomy and photography.

Note 1:  When you face south and watch the moon, it moves clockwise (left-to-right) in the sky.  Thus, you might expect the moon's right edge to enter shadow first.  But you can see that the shadow creeps up on the moon's left flank!  Can you understand why?  (Answer below).

Note 2:  While the moon is in partial eclipse, the part that is still in sunlight far outshines the part in shadow, even when only a sliver is lit by the sun.  It is hard to photograph the moon in partial eclipse, because the bright part completely dominates the dark part.  Only when the moon is fully lit or fully dark is it possible to adjust a camera to see all of its features.  The pictures from 11:15 - 12:30 were from the period of totality, when the whole moon was in shadow.  To illustrate the contrast of partial eclipse better, compare these two pictures.  They were both taken at 1:00, during partial eclipse, just with different camera settings:

Note 3:  If you didn't know there was an eclipse going on, and you looked at the sky at times like 10:45 or 12:45 above, you'd probably think it's just a normal moon in various phases.  At times like 10:15 or 1:15, it would look more unusual to you.  Can you express how and why? 

(Answers below)

First, a few pretty pictures:

Full moon over downtown LA, shortly before eclipse

Total eclipse. The star just above the moon was not visible before the eclipse.

Wisps of clouds over the moon as it is beginning to leave total eclipse 

Larger image of the total eclipse phase.

OK, answers to the notes above:

Note 1:  The apparent clockwise motion of the moon is only due to Earth's counterclockwise rotation.  This has nothing to do with the moon's motion.  The moon also spins counterclockwise (right-to-left) in its orbit around the Earth.  It's just that this motion is so slow (once / month as compared to once / day) that it is normally imperceptible.  The only times we get to observe the moon's true motion are during eclipses!  During this eclipse, we see the moon gradually cross Earth's shadow from right to left.

Note 3:  The moon's normal phases are a result of its being illuminated by the sun from various directions.  We are seeing the moon's shadow on itself.  When it is a crescent, both edges curve in the same direction (like a fingernail clipping or 10:45 above).  When it is gibbous or more than half-full, its edges bulge in different directions (like a football).  During eclipse, the shadow is cast by the Earth.  At times like 10:15 or 1:15 above, you see a moon that is more than half full but has fingernail-clipping curvature.  It looks unnatural, even if you're not sure why.       

Emergence Video

As the moon was just about to exit the totality of its eclipse, I thought that a video would be a more interesting way to capture the moment.  When I shot this little clip, it was very clear exactly when the moon was fully lit again, because it overwhelmed the camera.  I saw that the clip was just under two minutes long, which made me think of a certain piece of music that would be fitting in more ways than one.  I know it's cliche, but ...... couldn't help it!  This video is also posted to my YouTube profile as Lunar Eclipse: Dramatic finish set to music, April 15, 2014.