Saturday, October 10, 2015

Lunar Eclipse

Total lunar eclipse

Near the end of last month, the moon passed entirely through Earth's shadow, resulting in a full lunar eclipse. The moon didn't completely black out, due to sunlight scattering through Earth's atmosphere. Instead, the moon had a dim reddish-brown glow.

Of course, I took I lot of photos of this celestial phenomenon. I started taking photos during totality. I kept taking photos a couple times per minute, for a period of about 1.25 hours, until the moon was fully lit. My goal was to put the photos together, for an animation of the moon passing through the shadow of the Earth.

Partial lunar eclipse
"Fake" crescent
One thing I thought was pretty neat was when the partial lighting of the moon formed a perfect crescent. The crescent looked a lot like the waning crescent phase of the moon, but there was something strange about it. It reminded me of the artificial images of the moon that you'll see when you use a star-mapping program.

The reason is this: for a real crescent moon, the lighting comes from the left side, which causes a lot of shadows in craters along the lunar terminator. However, in this case, the craters had no shadows. There were also other differences caused by the way the moon was lit, but I won't go into those. It was essentially a full moon with a portion of it blacked out.

This is exactly what many night-sky programs do: they take a photo of the full moon, and black part of it out based on the phase.

Another thing I noticed was that, even after the shadow of the Earth was completely gone, the upper-left portion of the moon was still slightly dark. This was part of the penumbral shadow, which is caused by only a small portion of the sun being blocked by the Earth.

After the eclipse, I stitched the images together using GIMP. Because each image was taken in a slightly different direction, I had to align the images. I wasn't able to find a program that could do this automatically, so I did it manually. Finally, I created an animated GIF image using the aligned photographs:

High quality lunar eclipse animation

So that's my experience with the September, 2015 solar eclipse. Did you watch the eclipse? Comment below!

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