APOD: Mars and a Colorful Lunar Fog Bow (2010 Feb 02)

[APOD Robot]

Mars and a Colorful Lunar Fog Bow

Explanation: Even from the top of a volcanic crater, this vista was unusual. For one reason, Mars was dazzlingly bright two weeks ago, when this picture was taken, as it was nearing its brightest time of the entire year. Mars, on the far upper left, is the brightest object in the above picture. The brightness of the red planet peaked last week near when Mars reached opposition, the time when Earth and Mars are closest together in their orbits. Arching across the lower part of the image is a rare lunar fog bow. Unlike a more commonly seen rainbow, which is created by sunlight reflected prismatically by falling rain, this fog bow was created by moonlight reflected by the small water drops that compose fog. Although most fog bows appear white, all of the colors of the rainbow were somehow visible here. The above image was taken from high atop Haleakala, a huge volcano in Hawaii, USA.

<< Previous APOD

Discuss Any APOD

Next APOD >>

[/b]

[escherspace]

lunar fog bows (or moonbows) appear white to the naked eye because they are faint and are visible at night when our human eyes are much more more sensitive and see primarily in black and white. A photographic image of a moonbow with a long exposure will be able to distinguish the colors inherent in the moon's light which of course has the same spectrum as sunlight since as we all know, moonlight is simply reflected sunlight.

[verkle]

Something seems strange. If this photo was taken 2 weeks ago, then the moon would have a very new moon, and it is unlikely it could have made such a fogbow. Must be some sunlight in there, and the photo must be a composite.

[Indigo_Sunrise]

lunar fog bows (or moonbows) appear white to the naked eye because they are faint and are visible at night when our human eyes are much more more sensitive and see primarily in black and white. A photographic image of a moonbow with a long exposure will be able to distinguish the colors inherent in the moon's light which of course has the same spectrum as sunlight since as we all know, moonlight is simply reflected sunlight.

Of course, since Mr. Pacholka would never enhance his images, or take any sort of artistic license with them......

Something seems strange. If this photo was taken 2 weeks ago, then the moon would have a very new moon, and it is unlikely it could have made such a fogbow. Must be some sunlight in there, and the photo must be a composite.

Interesting note on the timetable.
A look through TWAN and it can be easily discerned that Mr. Pacholka's style is cleaned up, heavily processed, composite images.


*It is not my intent to be any sort of confrontational, I'm just not a fan of over-processed images. Sure, the images look pretty, but a little (more) realism wouldn't be a bad thing, either.

[neufer]

*It is not my intent to be any sort of confrontational, I'm just not a fan of over-processed images.
Sure, the images look pretty, but a little (more) realism wouldn't be a bad thing, either.

[mmontes]

A link on his site shows what appears to be the same image, unedited, with a typical fogbow. See
http://www.astropics.com/moonbow-haleakala-1393.html . Why would a longer exposure show separation of colors?

[Chris Peterson]

lunar fog bows (or moonbows) appear white to the naked eye because they are faint and are visible at night when our human eyes are much more more sensitive and see primarily in black and white. A photographic image of a moonbow with a long exposure will be able to distinguish the colors inherent in the moon's light which of course has the same spectrum as sunlight since as we all know, moonlight is simply reflected sunlight.

Solar fogbows also appear mainly white, which has nothing to do with our visual response. A fogbow does not show the full spectrum like a rainbow. The droplets are so small that diffraction effects cause spectral zones to overlap. Fogbows appear white with unsaturated red on on the outside and unsaturated blue on the inside. With lunar fogbows this is often seen with the eye, as long as the Moon is bright enough to get the fringe intensity above the photopic vision threshold. The slightly colored edges are almost always seen with solar fogbows.

[geckzilla]

A link on his site shows what appears to be the same image, unedited, with a typical fogbow. See
http://www.astropics.com/moonbow-haleakala-1393.html . Why would a longer exposure show separation of colors?

This picture is now the same picture as shown on the APOD but I saw it before it was changed and it didn't look like the same image. It looked like a different exposure entirely.

Is Wally lurking?

[Chris Peterson]

Something seems strange. If this photo was taken 2 weeks ago, then the moon would have a very new moon, and it is unlikely it could have made such a fogbow. Must be some sunlight in there, and the photo must be a composite.

Looking at the position of Mars, the image was made around January 20. That puts the Moon at a phase of 30%, which is more than sufficient to see a fogbow visually, let alone photographically. The azimuth of the fogbow is consistent with the position of the Moon at about 8pm; it would be in a completely different location if this was a solar fogbow made at about 3pm (when the solar altitude was right).

Like all of Wally's images, this is heavily processed. You either like the resulting aesthetics or not, but the image itself represents a real scene, not some sort of synthesized composite.

[Chris Peterson]

A link on his site shows what appears to be the same image, unedited, with a typical fogbow. See
http://www.astropics.com/moonbow-haleakala-1393.html . Why would a longer exposure show separation of colors?

This picture is now the same picture as shown on the APOD but I saw it before it was changed and it didn't look like the same image. It looked like a different exposure entirely.

Is Wally lurking? :wink:

Yeah, he changed that pretty quickly. The original image probably is much closer to what the eye would see. The current version has certainly had its saturation levels in the fogbow area cranked way up in Photoshop. I prefer the appearance of the original image, but the new one gives a better sense of the details of a fogbow- even if you'd almost never see it so saturated visually.

I'd say the oversaturated image is more scientifically interesting, but the original image is more aesthetically interesting.

[mmontes]

And yet both the original that looks like we would see, and this one both say "unedited". They look so similar, the one currently at his site and at APOD must have been edited with Photoshop or other software, right?

Given the fog, it is hard to see how you can end up with the image at APOD. The images at Optics Picture of the Day, and his the supporting web site, makes it difficult to understand how we'd see this. Of course, all astronomical images have certain hardware (filters) and software (selected RGB mappings) applied. It is good to put the information in the captions so folks know why it is the case that this fog bow appears different.

[Chris Peterson]

And yet both the original that looks like we would see, and this one both say "unedited". They look so similar, the one currently at his site and at APOD must have been edited with Photoshop or other software, right?

There is no doubt that some significant editing was applied. The simple fact that we saw two different versions proves that. All of Wally's images are heavily processed; almost none look at all like natural scenes. That said, I'm guessing that in this case "unedited" means this was a single shot, not a composite of some sort (like a stack of different exposures or a spatial mosaic).

Given the fog, it is hard to see how you can end up with the image at APOD.

It is certainly oversaturated, but overall the image looks pretty much like what you'd see with your eyes. Photographs made at night often show more color than the eye can see under the same conditions- we depend on that for astroimages, of course. Everything about this scene looks authentic to me.

[azm]

Since this is supposedly a photography site, images like this which are "heavily processed", digitally altered, to created wholly in photoshop should probably be identified as such. I'm sure the image is a composite of at least two digital photographic images, if not more. How much the photographs have been digitally altered to produce the rainbow colors, etc. is impossible to say without information from the phtographer. In any case, showing a field of stars against a blue sky, and a "star effect" image of Mars, while not identifying the "photograph" as an image processed/created in photoshop or similar software is really a misrepresention.

[Chris Peterson]

Since this is supposedly a photography site, images like this which are "heavily processed", digitally altered, to created wholly in photoshop should probably be identified as such. I'm sure the image is a composite of at least two digital photographic images, if not more. How much the photographs have been digitally altered to produce the rainbow colors, etc. is impossible to say without information from the phtographer. In any case, showing a field of stars against a blue sky, and a "star effect" image of Mars, while not identifying the "photograph" as an image processed/created in photoshop or similar software is really a misrepresention.

I disagree. The image shows a real scene, at a real time and place. It is substantially similar to what you'd have seen standing in that same spot at that time. Almost every image with astronomical content is highly processed. Cameras catch detail and color that the eye misses, and there is no requirement that an image be true to what the eye sees. It is only a misrepresentation when it stops portraying a real scene (as, for example, with the artistically fabricated Shasta-Lassen-Milky Way image a few weeks ago).

The APOD editors clearly like Wally's work. It is obviously polarizing: some people find it striking, others dislike it. That fact comes up on this forum every time one of his images is published. But those are aesthetic concerns. I've never seen anything to suggest that his images aren't accurate depictions of real places with accurate stellar patterns and positions. Whether you like the style or not, there is no evidence of any misrepresentation.

[mmontes]

Instead of "... all the colors of the rainbow were somehow visible here", should have said something like "careful digital processing of the image was able to show all the colors of the rainbow" and emphasized that it would not look this way to a person with a mark-1 eyeball.

A bit more care in writing the captions would be appreciated. Scientists have no trouble telling you what they've done to imagery.

[geckzilla]

I like most of Wally's photos. I have never seen a moon bow with my own eyes before so I'll just have to rely on Wally's photo.

Wally's attitude towards the criticism he receives may be warranted but I also think it's doing him a disservice. A little more transparency on some of the processes he uses would be enlightening. Right now we just have a bunch of people making assumptions about how he works and he's understandably jaded about it and doesn't bother responding. But those assumptions probably wouldn't happen as often if he there weren't unintentionally misleading statements such as "Unedited Photograph" under his work.

Wally's idea of "unedited" is unfortunately misguided especially when you consider the fact that he doesn't do his own Photoshop work but hires a shop to do it for him. How can he know what exactly editing means to people who are intimately familiar with Photoshop when he himself is admittedly ignorant about it? I really don't mean any disrespect at all, here. I think with a little more clarity most of Wally's technical criticizers could be assuaged. Of course, the aesthetic criticisms will remain.

[Chris Peterson]

Instead of "... all the colors of the rainbow were somehow visible here", should have said something like "careful digital processing of the image was able to show all the colors of the rainbow" and emphasized that it would not look this way to a person with a mark-1 eyeball.

Captions vary in quality, that's just the way of things with a daily image site. In this case, however, the existing caption is actually wrong, as is your suggested revision. All of the colors of the rainbow are NOT captured here, because no fogbow shows a full spectrum. What is visible is a diffuse white central zone, with red on the outside and blue on the inside. The reason that this color pattern occurs is well understood. What the caption should say is simply that careful processing has enhanced the red and blue fringes, making them more apparent than they would be likely to appear to the eye in a dim scene like this (they would, however, be very apparent in a solar fogbow).

[ChristianRR]

For this kind of picture (not taken through telescope), it would be good if APOD routinely indicated the digital processing that has been done to the image. For this one, just doing an "auto levels" in Photoshop would certainly boost the contrast and colors to what we see here, whereas in reality the "fog bow" would be much fainter. The flare on Mars also seems dubious, IMHO.

[geckzilla]

The flare on Mars also seems dubious, IMHO.

This is a completely unfounded statement. Flares happen all the time and there's no reason to think that the flare was added in this case any more than in any other instance.

[Chris Peterson]

Flares happen all the time and there's no reason to think that the flare was added in this case any more than in any other instance.

The flare is too large to be accounted for by a 6-vaned lens iris. Flared stars and planets are typical in Wally's images; I'm pretty sure he has said in the past he uses a photographic star filter to produce this effect.

[mmontes]

Right of course on the general statement about captions as well as what would be a better caption.

In order to write a satisfactory caption, the editors need enough information about the image and it's processing. A reading of the caption suggests that they did not have that. But I am unfamiliar with the image submission and caption writing process.

[neufer]

Something seems strange. If this photo was taken 2 weeks ago, then the moon would have a very new moon, and it is unlikely it could have made such a fogbow. Must be some sunlight in there, and the photo must be a composite.

Looking at the position of Mars, the image was made around January 20. That puts the Moon at a phase of 30%, which is more than sufficient to see a fogbow visually, let alone photographically. The azimuth of the fogbow is consistent with the position of the Moon at about 8pm; it would be in a completely different location if this was a solar fogbow made at about 3pm (when the solar altitude was right).

OK...so you have the moon & mars in about the right places.

So what about the asterisms? (Mars should be between Leo & Cancer.)

Can you identify a single asterism in the entire "photo"

Like all of Wally's images, this is heavily processed.
You either like the resulting aesthetics or not,
but the image itself represents a real scene,
not some sort of synthesized composite.

And you know this because... you have been assured of same
by the folks who do the photo-shopping on Wally's photo's?

[geckzilla]

Flares happen all the time and there's no reason to think that the flare was added in this case any more than in any other instance.

The flare is too large to be accounted for by a 6-vaned lens iris. Flared stars and planets are typical in Wally's images; I'm pretty sure he has said in the past he uses a photographic star filter to produce this effect.

Of course, I meant it wasn't "shopped" in. I should clarify that. But it's wrong to say that it's "dubious" ... like, what's dubious about it?

[geckzilla]

So what about the asterisms? (Mars should be between Leo & Cancer.)

Can you identify a single asterism in the entire "photo"

Fired up Stellarium, took a screenshot on January 20th 2010 and did a little overlay in Photoshop to compare. Sorry Art, the stars are really there. It all matches up perfectly. I don't know what asterisms you want so I drew the ones Stellarium provided over the stars. You can even see a nice open cluster of stars sitting in Cancer, there.

[Chris Peterson]

Can you identify a single asterism in the entire "photo"

I don't know about any asterisms. I see lots of recognizable stuff right where I expect it. You can't miss the Beehive cluster (M44) above Mars, sitting right in the middle of the little triangle made by gamma, delta, and eta Cancer (eta is just off the image at top). Below and to the left of Mars kappa and lambda Leo are very obvious. In the center, just above the fog, the head of Hydra is clearly seen (eta, delta, epsilon, rho, and zeta Hydra). Straight above the area between the two exposed peaks you can see the faint smudge of M48, another open cluster. Everything is right where it ought to be for the time and place.

The reason it can be fairly difficult to pick out constellations and asterisms in Wally's images is because he really flattens the contrast of his skies. As a result, there is only a little apparent difference in star brightnesses, even where the stars themselves are actually several magnitudes different.

And you know this because... you have been assured of same by the folks who do the photo-shopping on Wally's photo's?

I've looked closely at a lot of his images and never found anything "unphysical"; that is, all the objects are real and where they ought to be. In this particular case, I don't think we are looking at a composite simply because I've taken numerous similar images, and know that this is what a single exposure looks like. The stars are a little sharp for an untracked image, so it's possible that the sky was composited onto the foreground. If so, there's nothing wrong with that, since the image would still just show what was actually present. But my impression is that this is a single exposure.