Starship Asterisk*

by **alter-ego** » Sat Sep 20, 2014 6:05 am

abhagwat wrote: All of us have seen rainbow, moon-bow, glory, etc. But a sun-bow? This photo was taken by my friend Saee Nair in Melbourne on a cold July 2014 morning.

My experience is that a moon bow is a much less common event than what you've photographed, which appears to be a fairly common 22° halo. It's not a "bow" as in a rainbow or moon bow because they are seen when the light source is 180° from the arc's center (i.e. back lit wrt to the observer). A halo is viewed with the source in front of the observer at 0°, or at the center of the arc/circle.

Atmospheric Optics is a great website for all kinds of atmospheric phenomena. They have picture of the day too. A good halo picture might land there more so than here.

Edit:
I thought I'd add a bit more information about "sunbow". Wiki describes the sunbow as a circumzenithal arc (CZA). Atmospheric Optics also has nice pictures and discussion of the CZA. Although rare, the "sunbow" occurs near the zenith, but never completes a full circle and always when the sun is low in sky, i.e. never centered on the sun. A sunbow appears as an upsidedown rainbow.

Halos appear as circles around the sources, e.g. Sun and Moon. Their colors typically are red to pastel, but do not contain reds greens or blues (unlike the CZA which shows all colors). The reddish color is in the inside (sharp edge towards the sun) as your picture also shows.

Your picture shows all the attributes of a standard halo and It appears to be of the 22° type. Unfortunately, you have not captured a "sunbow" (CZA) but a nice picture for sure.

by **abhagwat** » Sat Sep 20, 2014 5:28 am

Would like to show you a photo of a sun-bow!

All of us have seen rainbow, moon-bow, glory, etc. But a sun-bow? This photo was taken by my friend Saee Nair in Melbourne on a cold July 2014 morning.

Interesting, is it not?

I hope APOD will display this photo soon on the NASA APOD website.

Thanks!

Anuradha Bhagwat

by **Nitpicker** » Wed Sep 10, 2014 2:49 am

In the first few minutes of 17-June-2014, in Hawaii (UT-10.0), the waning gibbous Moon (~75% illuminated, 4 days past full) was below 20° elevation, having been up for less than an hour and a half. The Moon would have been around 30° elevation at 1 am. (Note that Hawaii doesn't observe daylight saving.)

Edit: But the difference between PDT and HAST is indeed 3 hours. And based on the elevation of the visible stars in Leo, the local time must have been midnight.

by **geckzilla** » Wed Sep 10, 2014 2:08 am

Antony can give himself a pat on the back, now.

by **Rogelio Bernal** » Wed Sep 10, 2014 1:31 am

After double-checking my files, I can confirm that the time I took the picture was not around 3am but midnight. I relied on the EXIF data of the image files, and only yesterday figured that the time in the camera was still PDT (where I live). This means that back in June, if the EXIF says 3am, local Hawaiian time was three hours earlier. This puts the Moon near 30 degress above the horizon (looks about right in the 360 panorama image I posted the other day), and the stars are where they're supposed to. Apologies for any confusion my oversight may have caused.

In retrospect....It's very easy to lose track of time at a beach in Molokai after midnight

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.

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.

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.

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.

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?

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

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.

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

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

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???

:---[===] *

See Rogelio's comment above.

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???

:---[===] *

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.

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.

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

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

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?

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.

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 ...

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

Rogelio Bernal wrote:
geckzilla wrote:On July 17 ...
June 17

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.

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

geckzilla wrote:On July 17 ...

June 17

Starship Asterisk*

APOD: Moonbow Beach (2014 Sep 06)

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