APOD: Moonbow Beach (2014 Sep 06)

Comments and questions about the APOD on the main view screen.
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APOD: Moonbow Beach (2014 Sep 06)

Post by APOD Robot » Sat Sep 06, 2014 4:05 am

Image Moonbow Beach

Explanation: Like a rainbow at night, a beautiful moonbow shines above the western horizon in this deserted beach scene from Molokai Island, Hawaii, USA, planet Earth. Captured last June 17 in early morning hours, the lights along the horizon are from Honolulu and cities on the island of Oahu some 30 miles away. So where was the Moon? A rainbow is produced by sunlight internally reflected in rain drops from the direction opposite the Sun back toward the observer. As the light passes from air to water and back to air again, longer wavelengths are refracted (bent) less than shorter ones resulting in the separation of colors. And so the moonbow is produced as raindrops reflect moonlight from the direction opposite the Moon. That puts the Moon directly behind the photographer, still low and rising over the eastern horizon, a few days past its full phase.

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Re: APOD: Moonbow Beach (2014 Sep 06)

Post by geckzilla » Sat Sep 06, 2014 4:52 am

Rogelio is just like everyone else. He puts his pants on in the morning one leg at a time. Except, when he puts his pants on, he makes gold pictures.
Just call me "geck" because "zilla" is like a last name.

Antony Rawlinson

Re: APOD: Moonbow Beach (2014 Sep 06)

Post by Antony Rawlinson » Sat Sep 06, 2014 6:56 am

If it was early morning, then the (nearly) full moon would be setting, not rising. Checking Google Maps, I see that Molokai is to the east of Honolulu, so that makes this an evening picture, not a morning one. That agrees with the fact that in the days following full moon, the moon rises later - so the the sky would be sufficiently dark to show the stars as well as the rainbow from the moonlight.

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Re: APOD: Moonbow Beach (2014 Sep 06)

Post by geckzilla » Sat Sep 06, 2014 8:03 am

Antony Rawlinson wrote:If it was early morning, then the (nearly) full moon would be setting, not rising. Checking Google Maps, I see that Molokai is to the east of Honolulu, so that makes this an evening picture, not a morning one. That agrees with the fact that in the days following full moon, the moon rises later - so the the sky would be sufficiently dark to show the stars as well as the rainbow from the moonlight.
On July June 17 in Hawaii, the moon, a waning gibbous, just a bit over half75% full, was rising above the horizon in the east at around 5 3 AM. Looking west from Molokai, one would see the lights of Honolulu at 5 AM with the moon rising behind in the east.
Last edited by geckzilla on Sat Sep 06, 2014 8:16 am, edited 2 times in total.
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Rogelio Bernal

Re: APOD: Moonbow Beach (2014 Sep 06)

Post by Rogelio Bernal » Sat Sep 06, 2014 8:06 am

Antony Rawlinson wrote:... so that makes this an evening picture, not a morning one.
Hi Antony,

The picture was taken at exactly 3am local time on June 17, 2014. The moon was rising. About 40 degrees above the horizon.

I remember the time I spent at that beach that night very vividly. The cool thing is that the image on the APOD is actually a crop from a 360 degrees panorama, so you can have an idea about high high the moon was. . Here's the complete panorama for this scene - the moonbow is in the middle, and the moon is, obviously, that bright white "ball" all the way to the right:

Image

See? :wink:

Geckzilla, many times I wake up with the pants already on :mrgreen:

Cheers,
Rogelio

Rogelio Bernal

Re: APOD: Moonbow Beach (2014 Sep 06)

Post by Rogelio Bernal » Sat Sep 06, 2014 8:08 am

geckzilla wrote:On July 17 ...
June 17 8-)

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Re: APOD: Moonbow Beach (2014 Sep 06)

Post by geckzilla » Sat Sep 06, 2014 8:10 am

Rogelio Bernal wrote:
geckzilla wrote:On July 17 ...
June 17 8-)
My bad. I am falling asleep, here. I'm also thinking that Stellarium has a time zone issue since it's showing the moon just above the horizon at 5AM for me. Either way, the moon was rising and it was in the day's small hours.

Edit: It also might be a huge oversight on my part because I thought all this time Stellarium automatically adjusted time zones depending on where I had the location set but that does not seem to be the case. Hmm.
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Re: APOD: Moonbow Beach (2014 Sep 06)

Post by RedFishBlueFish » Sat Sep 06, 2014 1:01 pm

Striking panorama and APOD crop ... but perhaps would be more satisfying with the saturation slider a bit more to the left?

Yes, one knows and does accept, eye of the beholder ...

DrJoeS

Re: APOD: Moonbow Beach (2014 Sep 06)

Post by DrJoeS » Sat Sep 06, 2014 3:13 pm

That is a cool pic. I have never seen a moon rainbow. Next full moon, I will hope for rain and a chance to see one myself.

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Re: APOD: Moonbow Beach (2014 Sep 06)

Post by BillBixby » Sat Sep 06, 2014 6:26 pm

DrJoeS wrote:That is a cool pic. I have never seen a moon rainbow. Next full moon, I will hope for rain and a chance to see one myself.
Is this one of the things an eye will see, or does it require a camera with a longer exposure time and light gathering capabilities than the eye has?

Rogelio Bernal

Re: APOD: Moonbow Beach (2014 Sep 06)

Post by Rogelio Bernal » Sat Sep 06, 2014 7:37 pm

BillBixby wrote:Is this one of the things an eye will see, or does it require a camera with a longer exposure time and light gathering capabilities than the eye has?
You can see a moonbow with your own eyes when they're sufficiently bright, but the colors are hard to see - as it usually happens with anything low-light.

Cheers,
Rogelio

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Re: APOD: Moonbow Beach (2014 Sep 06)

Post by Ann » Sat Sep 06, 2014 8:00 pm

It's a great picture, but to me it is frustrating, too. When I see a lot of stars I always want to identify them, but in this picture I can't recognize a single asterism or constellation.

Can anyone help me?

Ann
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Re: APOD: Moonbow Beach (2014 Sep 06)

Post by alter-ego » Sat Sep 06, 2014 8:19 pm

Ann wrote:It's a great picture, but to me it is frustrating, too. When I see a lot of stars I always want to identify them, but in this picture I can't recognize a single asterism or constellation.

Can anyone help me?

Ann
I was a little disoriented too. The bundle of stars to the left of the clouds and above Honolulu is Coma Bernices. Midway between center and the right edge, above the peaked cloud formation, is the Little Dipper. Polaris clearly presented as the bright(est) star above and, slightly right of, the cloud peak.
Hope this helps.
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Re: APOD: Moonbow Beach (2014 Sep 06)

Post by alter-ego » Sat Sep 06, 2014 8:54 pm

geckzilla wrote: ...
It also might be a huge oversight on my part because I thought all this time Stellarium automatically adjusted time zones depending on where I had the location set but that does not seem to be the case. Hmm.
The correction is not automatic. I've defaulted to UTC (below), which is not always the most convenient, but most often used. Unfortunately, the time is still based off my system clock, i.e. I need to manually add 7 or 8 hours (PDT or PST) to get my current sky if I run in the UTC mode.
Stellarium Time Zone.JPG
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Re: APOD: Moonbow Beach (2014 Sep 06)

Post by Boomer12k » Sun Sep 07, 2014 1:26 am

What an interesting phenomena and a wonder picture,...could you see this with the naked eye, or is it camera only???

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Re: APOD: Moonbow Beach (2014 Sep 06)

Post by alter-ego » Sun Sep 07, 2014 3:12 am

Boomer12k wrote:What an interesting phenomena and a wonder picture,...could you see this with the naked eye, or is it camera only???

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See Rogelio's comment above.
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Re: APOD: Moonbow Beach (2014 Sep 06)

Post by BillBixby » Sun Sep 07, 2014 3:35 am

Rogelio Bernal wrote:
BillBixby wrote:Is this one of the things an eye will see, or does it require a camera with a longer exposure time and light gathering capabilities than the eye has?
You can see a moonbow with your own eyes when they're sufficiently bright, but the colors are hard to see - as it usually happens with anything low-light.

Cheers,
Rogelio
Thank you for both the picture and the answer.

Bill

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Re: APOD: Moonbow Beach (2014 Sep 06)

Post by Ann » Sun Sep 07, 2014 5:19 am

alter-ego wrote:
Ann wrote:It's a great picture, but to me it is frustrating, too. When I see a lot of stars I always want to identify them, but in this picture I can't recognize a single asterism or constellation.

Can anyone help me?

Ann
I was a little disoriented too. The bundle of stars to the left of the clouds and above Honolulu is Coma Bernices. Midway between center and the right edge, above the peaked cloud formation, is the Little Dipper. Polaris clearly presented as the bright(est) star above and, slightly right of, the cloud peak.
Hope this helps.
Thank you so much, alter-ego. Yes, that bundle of stars looks quite a lot like the big, spread-out Coma Berenices. But according to my software, Coma Berenices and Ursa Minor are rather far apart in the sky. Importantly, the Big Dipper is between Coma Berenices and the Little Dipper with Polaris. In other words, we ought to see the Big Dipper here.

But maybe the Big Dipper is behind that big cloud?

Ann
Last edited by Ann on Sun Sep 07, 2014 11:52 pm, edited 1 time in total.
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Re: APOD: Moonbow Beach (2014 Sep 06)

Post by alter-ego » Sun Sep 07, 2014 5:54 am

Ann wrote:
alter-ego wrote:
Ann wrote:It's a great picture, but to me it is frustrating, too. When I see a lot of stars I always want to identify them, but in this picture I can't recognize a single asterism or constellation.

Can anyone help me?

Ann
I was a little disoriented too. The bundle of stars to the left of the clouds and above Honolulu is Coma Bernices. Midway between center and the right edge, above the peaked cloud formation, is the Little Dipper. Polaris clearly presented as the bright(est) star above and, slightly right of, the cloud peak.
Hope this helps.
Thank you so much, alter-ego. Yes, that bundle of stars looks quite a lot like the big, spread-out Coma Berenices. But according to my software, Coma Berenices and Ursa Minor are rather far apart in the sky. Importantly, the Big Dipper is between Coma Berenices and the Little Dipper with Polaris. In other words, we ought to see the Big Dipper here.

But maybe the Big Dipper is between that big cloud?

Ann
Hi Ann,
Yes the cloud(s) are making it difficult to identify stars. The Big Dipper handle is visible, but 3 of the bowl stars are not. I believe the right side of the image contains Errai and Alfirk (Cepheus), but the star field does not completely add up. I'm attributing that confusion to the less dense, but still problematic, clouds.
Edit: FYI, Dubhe is the one bowl star visible.
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Rogelio Bernal

Re: APOD: Moonbow Beach (2014 Sep 06)

Post by Rogelio Bernal » Sun Sep 07, 2014 7:53 am

Yes, the Big Dipper is right in the middle of the image, above and to the right of the moonbow. Only one bowl star and three handle stars are visible, as alter-ego said. The "bundle of stars" is indeed Coma Berenices. Also, the tail of Leo is visible right above the lights from O'ahu. It is confusing because star brightness differences aren't very obvious, there's some lens distortion (the Little Dipper appears just a tad smaller than the Big Dipper), and of course, the clouds covering some of the patterns that are easiest to identify.
Thanks,
Rogelio

Antony Rawlinson

Re: APOD: Moonbow Beach (2014 Sep 06)

Post by Antony Rawlinson » Sun Sep 07, 2014 8:57 pm

geckzilla wrote:
Antony Rawlinson wrote:If it was early morning, then the (nearly) full moon would be setting, not rising. Checking Google Maps, I see that Molokai is to the east of Honolulu, so that makes this an evening picture, not a morning one. That agrees with the fact that in the days following full moon, the moon rises later - so the the sky would be sufficiently dark to show the stars as well as the rainbow from the moonlight.
On July June 17 in Hawaii, the moon, a waning gibbous, just a bit over half75% full, was rising above the horizon in the east at around 5 3 AM. Looking west from Molokai, one would see the lights of Honolulu at 5 AM with the moon rising behind in the east.
I'm not clear why a gibbous moon would rise after midnight. Wouldn't a moon rising at 3am and still low enough in the sky at 5am to create a rainbow, be well into the crescent phase?

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Re: APOD: Moonbow Beach (2014 Sep 06)

Post by geckzilla » Sun Sep 07, 2014 9:01 pm

Antony Rawlinson wrote:I'm not clear why a gibbous moon would rise after midnight. Wouldn't a moon rising at 3am and still low enough in the sky at 5am to create a rainbow, be well into the crescent phase?
The moon doesn't change phase that quickly. The next night, it was around 60% illuminated. The night after that, just under 50%. It would never go from being gibbous to being a crescent in a single night.
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Antony Rawlinson

Re: APOD: Moonbow Beach (2014 Sep 06)

Post by Antony Rawlinson » Sun Sep 07, 2014 9:24 pm

geckzilla wrote:
Antony Rawlinson wrote:I'm not clear why a gibbous moon would rise after midnight. Wouldn't a moon rising at 3am and still low enough in the sky at 5am to create a rainbow, be well into the crescent phase?
The moon doesn't change phase that quickly. The next night, it was around 60% illuminated. The night after that, just under 50%. It would never go from being gibbous to being a crescent in a single night.
No - the moon changes phase in sync with the change in time of moonrise. My understanding is that the full moon rises at sunset - i.e. around 6pm in the tropics. As it progresses to later phases, it rises later and later; it reaches half-phase about 7 days after full phase, and at this point in the cycle, moonrise is at midnight. Is this not correct?

I don't know where you see the suggestion that the change happens in a single night.
Rogelio Bernal wrote:
Antony Rawlinson wrote:... so that makes this an evening picture, not a morning one.
Hi Antony,

The picture was taken at exactly 3am local time on June 17, 2014. The moon was rising. About 40 degrees above the horizon.

...

Cheers,
Rogelio
I've now seen Rogelio's reply -so it's a bit earlier in the morning than suggested above. I'm still a bit surprised that a moon just days after full-phase would still be rising that much time after midnight, but it's not a big point.

It's a great picture, anyway.

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Re: APOD: Moonbow Beach (2014 Sep 06)

Post by Chris Peterson » Sun Sep 07, 2014 9:24 pm

Antony Rawlinson wrote:I'm not clear why a gibbous moon would rise after midnight. Wouldn't a moon rising at 3am and still low enough in the sky at 5am to create a rainbow, be well into the crescent phase?
The Moon didn't rise at 3am. It rose a little before midnight. The image was made at 3am with the Moon at an elevation of 40°, closer to the meridian than the horizon. And because the Moon isn't on the ecliptic plane, its phases can't be perfectly correlated to the horizon. But you're right, you couldn't have a gibbous Moon rising in Hawaii at 3 am.
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Re: APOD: Moonbow Beach (2014 Sep 06)

Post by geckzilla » Sun Sep 07, 2014 9:29 pm

Antony Rawlinson wrote:
geckzilla wrote:
Antony Rawlinson wrote:I'm not clear why a gibbous moon would rise after midnight. Wouldn't a moon rising at 3am and still low enough in the sky at 5am to create a rainbow, be well into the crescent phase?
The moon doesn't change phase that quickly. The next night, it was around 60% illuminated. The night after that, just under 50%. It would never go from being gibbous to being a crescent in a single night.
No - the moon changes phase in sync with the change in time of moonrise. My understanding is that the full moon rises at sunset - i.e. around 6pm in the tropics. As it progresses to later phases, it rises later and later; it reaches half-phase about 7 days after full phase, and at this point in the cycle, moonrise is at midnight. Is this not correct?

I don't know where you see the suggestion that the change happens in a single night.
I read your post several times to try to understand what you meant and that's what I took away even though I couldn't see why *anyone* would think that. Anyway, the confusion here is that by "moonrise" you mean the moment it rises above the horizon. I took this to mean only that it was in the process of rising.
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