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John Boudreau
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Reged: 04/06/08

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Re: Ashen Light - Redux new [Re: azure1961p]
      #5766072 - 03/30/13 02:30 AM

It's quite common for a planetary imager to blacken a final result's background to a blackpoint of 0 in software. This is usually done in PhotoShop by either making a selection mask of the planet with a copy of the image, or since some planets like Venus are essentially round, by simply drawing a circular mask around the planet's limb. Then the sky background is converted to a level of 0 without effecting the planet's disk itself.

I've attached a strongly stretched version of Wayne Jaescke's image.

***Edit on 4/1: Note that I've deleted that stretched version of Wayne's image since it has served it's purpose as my analysis has been supported by Wayne himself in a follow-up post.

In this case, it appears Wayne had square-cropped the full RGB frames earlier as the dark part of the disk has a straight slice cut off vertically along the RH side. Then it appears that he used a circular mask to separate the background before dropping the blackpoint there. What you see as weak light on the dark side is background noise that had been included in the circular mask used to protect the planet. There is some darkened separation along the terminator that had to be done with a phase-shaped selection mask which puzzles me, but perhaps this was simply pasted over a circular-mask selection version he had done earlier. I'll drop him a PM and see if he recalls.

A couple of reasons for doing this include simply making a clean, black background for text in versions used in ALPO/BAA reports. Or because even keeping a very dark, noisy background would unnecessarily add to file size vs. a 0-blackpoint darkened background. Some guys use a sharp edged mask, others feather the edges a few pixels to blend the mask smoothly between planet and background. The result is then centered/pasted into a black frame used for presentation.

I usually blend the mask a few pixels and darken to 0, but in some cases it's best to leave the real background alone if it tells a tale itself. I always save early steps in processing with the noisy sky background if it's needed for review, BTW. My 1-micron thermal image GIF of the darkside of Venus on two nights linked earlier in this thread is one such image left that way even in the final result to show the glare/reflection pattern and a background star in one of the frames--- the same thing should be done with any serious Ashen Light imaging attempts too. Another example is a near-IR image of Uranus where the background demonstrates an accurate orientation of the planet by way of the position of a couple of moons--- that background was actually enhanced because the moons were not detected at the processing settings used for Uranus itself. In other words, I did use a mask for that image but brightened the background instead of darkening it.

http://alpo-j.asahikawa-med.ac.jp/kk12/v120524a1.gif

http://alpo-j.asahikawa-med.ac.jp/kk12/u120917b1.jpg

Edited by John Boudreau (04/01/13 08:30 AM)


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Rick Woods
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Reged: 01/27/05

Loc: Inner Solar System
Re: Ashen Light - Redux new [Re: John Boudreau]
      #5766090 - 03/30/13 02:52 AM

John,

Those are reasons I don't believe imaging can be accepted as the final word in these matters; it's too influenced by the methods used by the imager to produce the final product. A little creative processing can erase many important features, if one isn't being strictly objective (as you obviously are), in order to create a more impressive image.

As an aside, I can't help notice how closely your image of Uranus agrees with the sketches Stanislaus-Jean has been posting.


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buddyjesus
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Re: Ashen Light - Redux new [Re: Rick Woods]
      #5766099 - 03/30/13 03:02 AM

very interesting. i learned a lot. Like I shouldn't look into AP cause it is too technical for me. haha. In all seriousness though, thanks for explaining what I saw in the image for me.

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stanislas-jean
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Reged: 10/22/08

Re: Ashen Light - Redux new [Re: buddyjesus]
      #5766145 - 03/30/13 04:23 AM

The question through this kind of method used for imaging remains
This suppose if the m10 star revealed on the venus picture that the stretching is still linear in order to keep the same scaling on the planet.
Are we sure of this?
If this is the method is a serious assessment.
Anyway at final through the manipulations, it would be interresting to test with the chipset to which light level it can be reached some light with the same exposure conditions and scope. To see by a parallel assessment the pertinence.
Stanislas-Jean


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swalker
Imaging Editor - Sky & Telescope
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Reged: 01/22/07

Loc: 42.9225°N, 71.2242°W
Re: Ashen Light - Redux new [Re: stanislas-jean]
      #5766283 - 03/30/13 08:18 AM

Rick, an image presented as a "pretty picture" result is just that,massaged to produce the most visually appealing result. However, imagers should be both keeping their raw, unadulterated data and their notes for important observations such as these for actual scientific analysis. Pulling an image from a forum and manipulating it to bring out "hidden detail" is asking for trouble. This is exactly what bigfoot hunters and UFO believers do, which compounds the problem rather than reveals any hidden secrets.

Back to the question at hand, I've posted my results from my imaging campaign last year trying to detect the rumored ashen light in images. I had negative results, but should note the evening posted (5/18/2012) I had recieved an alert on an Ashen Light sighting, and amazingly it was clear here in NH. I observed the planet visually both before and after shooting through the scope, so I was not surprised at all to record nothing surprising that evening. I know it's not going to convince the believers, but it certainly convinced me. Additionally, I have spent 5 years studying Venus both photographically and visually. I have myself seen some interesting optical illusions which I describe in the other thread in the imaging forum, which only reinforced my skepticism.

Finally, there is just no way that the phenomena, if it exists, can't be photographed: John's and Christophe's images of the thermal emissions from the surface of Venus clearly demonstrate that although the illuminated crescent does create reflections and artifiacts, it does not obliterate the signal from the unilluminated side. So I still believe that if the phenomena exists, it can be photographed. But I'll leave that to others, as I made three concentrated attempts under excellent conditions, in a favorable apparition.


Edited by swalker (03/30/13 08:36 AM)


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stanislas-jean
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Reged: 10/22/08

Re: Ashen Light - Redux new [Re: stanislas-jean]
      #5766533 - 03/30/13 11:13 AM

Personnally on the 18th May 2012 the weather was not favorable here, but reported on the 13th.
Anyway, I am also convinced that if AL exists this could be captured by imaging and not shall be.
This is the only method that can do in this way.
However beyond the fact that the treatment may be linear, stretched, etc... I object the fact that we donot know where we are about the light levels in terms on number of cd/m2.
It is mandatory to know this because we will continue to speculate about.
We have to perform a comparison between visual and ccd capture methods that are not quite similar it seems (one for UFO and one for blind, sorry for the imagers from my opinion pertinent).
Otherwise I am conducting to think that even the 3K fossil light of the universe will not exist because with 3sec of exposure at F24 and with the scope X it is not captured.
Light level: how many cd/m2 or any other unit?
Answer is O?: this is wrong because with light reflexion by planets to venus dark side, this is producing a light level not at O level (something as rather the mili lux level). Discussion at the beginning of the forum and Mardi's proposal. This should be on the chipset and this is not.
Stanislas-Jean


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swalker
Imaging Editor - Sky & Telescope
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Reged: 01/22/07

Loc: 42.9225°N, 71.2242°W
Re: Ashen Light - Redux new [Re: stanislas-jean]
      #5766641 - 03/30/13 11:46 AM

It's not my problem to educate you on the functionality of digital cameras or myriad data analysis techniques, nor decipher your poorly translated posts.
I'm not claiming that I closed the book on the phenomena, just that I have satisfied myself with my attempts at capturing it.


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stanislas-jean
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Reged: 10/22/08

Re: Ashen Light - Redux new [Re: swalker]
      #5766765 - 03/30/13 12:16 PM

You satisfied yourself very well, however some quantified assessment remains welcome.
John get views with a m10 star not far to the planet sothat we have comparison elements in order to evaluate a certain light level on the dark side, in the wavelength reported.
From your results we remain blind and stetched linearly.
Stanislas-Jean


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Rick Woods
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Reged: 01/27/05

Loc: Inner Solar System
Re: Ashen Light - Redux new [Re: stanislas-jean]
      #5766830 - 03/30/13 12:58 PM

OK, let's be civil, you guys. I don't want this thread getting shut down just when some interesting people are weighing in. There's nothing personal in this topic, and no need for anyone to be sarcastic. We all want the same thing; to figure out what's going on.

If the AL is an illusion, why has it been seen by so many first-rate observers over the years - people who know all about optical illusions? If illusion, what is its nature? If real, and it can't be/hasn't been imaged, why not? And, is anyone actually sure it hasn't ever been imaged?

Also: is everyone talking about the same thing as Ashen Light? I've variously seen the phenomenon described as the continuation of the cusp all the way around Venus; lighter reddish-brown markings appearing in the unlit hemisphere; now, someone referred to a darkening of the unlit side. What's the absolute definition of Ashen Light?


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stanislas-jean
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Reged: 10/22/08

Re: Ashen Light - Redux new [Re: Rick Woods]
      #5766868 - 03/30/13 01:19 PM

This will be kept honestly, Rick.
What I cannot admit is the fact that according the Mardi' proposal (reflexion of light by planet atmospheres on the venus dark side), the light amount created should be revealed by ccd with the procedures given through the previous posts.
And this is not on visual wavelength.
As a consequence I am wandering of which light levels the ccd procedures in use can reach (the 3K fossil light of the universe?).
Photometry is not a concern, it is, quantified.
This is the node.
Stanislas_Jean


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WayneJ
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Re: Ashen Light - Redux new [Re: stanislas-jean]
      #5766995 - 03/30/13 02:45 PM

I just wanted to chime in on the image of mine that was posted earlier in this thread. John was completely accurate in his analysis of the processing, but I also wanted to add that the image was taken in daylight, so the background of the UV channel was much brighter than that of the IR channel. The background was cropped for aesthetics. Anyone wishing to analyze any of my data for scientific purposes should let me know.

That said, there was no visible-light component to that image -- it's a UV(G)IR image made through an Astrodon UVenus filter and Astronomik Pro Planet 805nm filter -- thus there is no value in analyzing it with regard to the Ashen Light phenomena.

With regard to the AL phenomena, I've been an observer for nearly 40 years and have never seen it, despite many visual and photographic efforts to capture it. I will, however, remind my fellow visual observers that there are those who will swear that they've seen bigfoot, UFOs, and a second-shooter on the grassy knoll. As the old saying goes, extraordinary claims require extraordinary proof. As the AL phenomena continues to elude photographic proof, despite consistent and rapid advancement in imaging technology, makes the claim of the AL as a real phenomena that much more 'extraordinary' in my opinion. Further, given that numerous space based probes have failed to locate any phenomena that supports the 'legend' of the AL makes visual observation claims of this phenomena more extraordinary.

Regards,

Wayne


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stanislas-jean
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Reged: 10/22/08

Re: Ashen Light - Redux new [Re: WayneJ]
      #5767034 - 03/30/13 03:05 PM

Yes Mr Wayne I read you with interest.
CCD results are a pertinent objection to AL light existence.
But, regarding the light level created by the light reflexion of solar light from solar planets (earth moon,...) on the venus dark side can be calculated to an amount that is true and existing (some evaluated to be 0.001cd/m2 around).
So why this is not recorded by CCD?
This is the objection.
Where this is wrong?
Stanislas-Jean


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azure1961p
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Reged: 01/17/09

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Re: Ashen Light - Redux new [Re: Rick Woods]
      #5767173 - 03/30/13 05:03 PM


Rick,

I think it goes to prove (perhaps) that even knowledge and understanding of an optical illusion isn't enough to disolve or prevent its recurrence but just reconciliation in the nature of the phenomenon. I can literally produce an ashen-lite-like illusion even though I kno its false. I've seen it in nature manmade and natural. My assertion is its the eye/brain filling in on the suggestion of a shape or pattern.

While its unfortunate a select few greet the finds of the three imagers like so much garlic for Dracula, I think its a liberating tool for visual observers.
It can help define boundaries while also opening potential challenges for observing projects and programs simply because by virtue of the information rich results. I'm convinced if there were less resistance to technology by some dyed in the wool visual observers (of which Im one) the debate would be more productive. When the arguments against CCD as a tool bog down in tedious evasive writhings it becomes posture over substance and it debases validity.

Rick Ive enjoyed the thread for the greater part. That these fellas weighed in was appreciated. I'm glad you redux'd even if Im still wanting in terms of evidence.

Pete


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buddyjesus
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Reged: 07/07/10

Loc: Davison, Michigan
Re: Ashen Light - Redux new [Re: azure1961p]
      #5767671 - 03/30/13 09:36 PM

I would like for it to stay civil also. This thread has been the most civil in regards to an controversial phenomenon as I have seen on CN.

WayneJ, sorry for posting without your permission. I figured it would be cool but wasn't sure as it was noncommercial/educational use and credit was given. If the mods or you wish to remove feel free. I didn't know how to link to just his post and not the top of the thread. Please excuse my ignorance.

now I don't know imaging, but I have a question just out of curiosity as I feel it pertinent to add to the continued discussion. Would the background noise be eliminated with a dark balance or a white balance? Thanks for any input.


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GlennLeDrew
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Re: Ashen Light - Redux new [Re: azure1961p]
      #5767692 - 03/30/13 09:47 PM

Regarding attempts at imaging.

Perhaps one way to at least mitigate against the great glare from the sunlit crescent is to, in quick succession, obtain images of identical duration with and without Venus in the FOV. By this measure, one should have an 'uncontaminated' base image of the sky glow, which could be used as a reference for subtraction of the glare.

Note, I'm just blue-skying here; I'm not sure if such an approach would be viable. And if it is, even with the use of an occulting device such technique might still be worth doing, for there will still be scatter of the bright Venusian light as it transits the optical system, introducing veiling glare of some extent.

All to provide the best case scenario for the detection of the ashen light.

This notwithstanding, I feel that if the ashen light is real, and visible to the eye in spite of the glare if the sunlit crescent, then it *must* be recordable without having to go to extraordinary lengths or employ near wizardry. After all, the camera is no worse affected by glare than is the eye. And it's so easy to stretch and process an image to bring out subtle features, without introducing spurious, doubt-inducing artifacts. As long as the exposure is sufficient to bring the sky glow well enough above the level of instrumental noise.

This is not difficult to achieve, for the sky will be no darker than about 19 magnitudes per square arcsecond. And so an exposure of around the half-minute range should suffice, unless the f/ratio is rather large. Here is where a large aperture helps; it provides good image scale at a faster f/ratio.

Unlike Stanislas-Jean's concerns, if detection is the aim, it's not necessary to know what the illumination level is. Even if of extraordinary faintness, it must perforce be a little brighter than sky glow, for the light of the sky always adds to the light of the object seen through it. The only concern is maximizing contrast transfer so as to have a hope of detection if the AL is intrinsically fainter than sky glow by more than about 4-5 magnitudes. (For example, if fainter than the sky by 5 magnitudes, it is 1/100 as bright, and so this feeble light, when added to the foreground sky glow, makes for a source 1% brighter than the sky; pretty low contrast.)


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WayneJ
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Re: Ashen Light - Redux new [Re: GlennLeDrew]
      #5767837 - 03/30/13 11:11 PM

Quote:

WayneJ, sorry for posting without your permission. I figured it would be cool but wasn't sure as it was noncommercial/educational use and credit was given. If the mods or you wish to remove feel free. I didn't know how to link to just his post and not the top of the thread. Please excuse my ignorance.




I have no objections to the manner in which you used my image It's fully consistent with the Creative Commons use-license that I have on my website.


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buddyjesus
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Re: Ashen Light - Redux new [Re: WayneJ]
      #5767883 - 03/30/13 11:33 PM

that is what I thought. thanks

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stanislas-jean
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Reged: 10/22/08

Re: Ashen Light - Redux new [Re: GlennLeDrew]
      #5768048 - 03/31/13 03:28 AM

I read all the posts emitted during night.
I recognise that the ccd procedures constitute a step more for an explanation.
However, may I insist on the fact of the, you remember Glenn of the assessment regarding lighting created by light planet reflexions), such AL must be collected by the procedure explained. This is creating a sufficient light level because John showed a M10 magnitude star (in NIR), why not in white light, an others nothing in other light fields, against the backgound sky of m18 as you wrote.
This kind of AL light must be recordable in white light because the amount of light is sure and existing, not hypothetic, , not accessible to eye, and, evaluated to be around 0.001cd/m2.
The 2 way approaches cannot be crossed for making something convergent for the moment.
Stanislas-Jean


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Cotts
Just Wondering
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Reged: 10/10/05

Loc: Toronto, Ontario
Re: Ashen Light - Redux new [Re: WayneJ]
      #5768795 - 03/31/13 01:24 PM

Quote:

Quote:

WayneJ, sorry for posting without your permission. I figured it would be cool but wasn't sure as it was noncommercial/educational use and credit was given. If the mods or you wish to remove feel free. I didn't know how to link to just his post and not the top of the thread. Please excuse my ignorance.




I have no objections to the manner in which you used my image It's fully consistent with the Creative Commons use-license that I have on my website.




If you want to post a link to a photo on CN, look at the box immediately below where you are typing your post. You will see a box entitled "Instant UBB Code. In that box click on the 'URL' link. A dialog box will appear. Paste the URLof the picture there and press ok. Another dialog box will appear where you can type something like 'Wayne's Venus Pic' and press ok again. Now your link will appear in your post in underlined green saying "Wayne's Venus Pic" instead of a hundreds of characters long, ugly URL.

Easy once you've done it a couple of times.

Wayne, you were most kind to give permission after the fact but our TOS trumps that. To post a pic not your own, post a link. Saves difficulties that did not arise here but can and have happened on CN in the past.

As you were,

Dave


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swalker
Imaging Editor - Sky & Telescope
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Reged: 01/22/07

Loc: 42.9225°N, 71.2242°W
Re: Ashen Light - Redux new [Re: Cotts]
      #5770315 - 04/01/13 09:20 AM

This is an interesting discussion, though admittedly frustrating. Stanislas-Jean, one can easily determine the background sky brightness from my original data not by recording a star (which all but the brightest were invisible at the time I shot- the Sun was still up), but simply calculating the mean value of the background signal in the test exposures I conducted on images with no planet or other subjects in the field using the same exposures that evening immediately preceding my images. Also, comparing John's near-infrared image that serendipitously captured a star in the field is folly: in near-infrared light, one can detect many stars in broad daylight. Indeed, many objects are more visible in near-infrared light during the day. In January of 2007, I recorded comet McNaught as it was cosest to the Sun using the same technique as John. But star brightness values in near-infrared light rarely if ever correspond to the visual magnitude estimates published in star charts for two obvious reasons: near infrared light is invisible to the human eye, and many stars are far brighter in wavelengths beyond the range of human vision.

That said, many of the historical sightings of ashen light were seen in broad daylight, particularly Dale Cruikshank's memorable observation by a similar-sized telescope (12-inch Newtonian)in 1962. My campaign was meant to duplicate what I felt was the most credible sighting in recent history.

I have not posted even deeper exposures I took through un-filtered light that night, where the over-exposed region of the planet bleeds much more into the planet's un-illuminated region (recorded at 3.75 frames per second using the same camera and setup, gain at 0) because they also show nothing.

Again, I state that I visually observed the planet both before and after my images, and continued to observe as the sky darkened. But because I failed to detect any sign of a glow as twilight deepened, I determined that further imaging would prove fruitless on each of the three nights.

To answer an earlier question, I believe the term "ashen light" refers to the sighting of a faint glow within the disk of the planet, not simply the extended or even connected "cusps" of the back-illuminated atmosphere.

I continue to remain skeptical of all ashen light sightings. Perhaps I'll try again in the next favorable elongation from my latitude; it really does not take much more additional time or effort when trying to capture "pretty" images on the same nights.


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