Back in May I posted pictures of Mercury's sodium tail. The moon has one too, thought to be mostly generated by micrometeorite impact. It is fainter than Mercury's, but can be easier to see at new moon. At this time, especially near astronomical midnight, we are looking down the long axis of the tail, increasing it's optical density considerably. Also, earth's gravity is thought to somewhat focus the tail, further aiding observation. It is still quite faint, but we were able to image it this weekend after several unsuccessful summer attempts. The anti-solar point at midnight is almost directly overhead here during winter, which helps a lot. Images were taken with a DSLR and 24mm lens, using a 10 nm bandpass sodium filter (589 nm). I should note that all the sodium vapor lamps around town don't really help this effort!
I attached two images. The first is from 12/3, about 2 hours before new moon. It is relatively unprocessed, and the spot can barely be seen between the Pleiades and the Hyades. It's big - about 2.5-3 degrees across. The second is much more processed (and hence noisy) in order to be able to better see the motion of the spot along the ecliptic between 12/3 and 12/4 (the latter being about 22 hours after new moon). Neither image will win awards but we're very happy with these as proof-of-principle images. We'll use what we learned from this and hopefully get better pictures in January. I may have to splurge on an imaging quality filter with narrower bandpass!
Lunar sodium tail
Moderator: Montana
Re: Lunar sodium tail
Hi,
Thanks for sharing the images. I had no idea that the Moon had trail. You learn something new every day. Good luck in Jan, hope you have clear skies.
John
Thanks for sharing the images. I had no idea that the Moon had trail. You learn something new every day. Good luck in Jan, hope you have clear skies.
John
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Re: Lunar sodium tail
Wow! amazing images, I didn't know about this either
Could you add an annotated version to describe what we are seeing the images? I think I am looking at the right place but not sure. Also, why is there a halo, is this a 365 degree image?
Alexandra
Could you add an annotated version to describe what we are seeing the images? I think I am looking at the right place but not sure. Also, why is there a halo, is this a 365 degree image?
Alexandra
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Re: Lunar sodium tail
Thanks John and Alexandra!
Alexandra - there is severe vignetting since the clear aperture of our sodium filter is somewhat less than the lens aperture. The first image is pretty close to how it appeared on the camera screen. The second was extreme processed to better show night-to-night motion of the spot along the ecliptic (which helped us be confident that this was the sodium spot and not some artifact or cloud, since nothing was changed with the equipment setup (such as filter orientation)), but this also introduced LOTS of noise and a brightness gradient. I'll continue to work on the processing, and post another hopefully cleaner version that includes annotations.
I guess I should also have clarified that the tail is formed by radiation pressure, like a comet tail. The sodium has very strong resonant light scattering at 589 nm.
Kevin
Alexandra - there is severe vignetting since the clear aperture of our sodium filter is somewhat less than the lens aperture. The first image is pretty close to how it appeared on the camera screen. The second was extreme processed to better show night-to-night motion of the spot along the ecliptic (which helped us be confident that this was the sodium spot and not some artifact or cloud, since nothing was changed with the equipment setup (such as filter orientation)), but this also introduced LOTS of noise and a brightness gradient. I'll continue to work on the processing, and post another hopefully cleaner version that includes annotations.
I guess I should also have clarified that the tail is formed by radiation pressure, like a comet tail. The sodium has very strong resonant light scattering at 589 nm.
Kevin
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Re: Lunar sodium tail
Here's an annotated version with less extreme processing. The line shows the ecliptic, and east is to the left. The circles indicate the shifting position of the spot along the ecliptic.
Kevin
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Re: Lunar sodium tail
Amazing. Well done !!
Christian Viladrich
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Re: Lunar sodium tail
fantastic post and images, well done
Pedro Re'
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Re: Lunar sodium tail
Remarkable image!
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