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stanislas-jean
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Re: Ashen Light - Redux [Re: buddyjesus]
      #5744504 - 03/20/13 04:41 AM

Interresting Buddy, this bring a lot on the subject.
Is there something was performed on Mercury from your informations with the Keck or some other big guns?
It is strange that on Mercury, from my observations, nothing such was reported. It is harder to observe Mercury but the reports are the reports.
I agree with you, more observationnal data are needed for making a straight conclusion.
Pete, the fact that with ccd chipset, if with 1s, 10s, 30s etc exposure time nothing is collected, this doesnot mean that AL is not existing but again that a certain amount of light cannot be captured with such exposure. Beyond 30s, light glare is very present and disturbing so that the capture method has to be very expected acurate.
Also the duality eye-ccd properties cannot be straightforward so easily.
Is there somebody who knows where to find ephemeris of the solar wind reaching planets (here for Venus)? or this is confidential.
Stanislas-Jean


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azure1961p
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Re: Ashen Light - Redux new [Re: stanislas-jean]
      #5745231 - 03/20/13 02:08 PM

You need to try some imaging Stan there is no hiding place with a DMK DBK Flea3 Toucam or the like. Your assumptions are more in line with Tri-X.

Pete


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stanislas-jean
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Re: Ashen Light - Redux new [Re: azure1961p]
      #5745323 - 03/20/13 02:55 PM

Just 2 or may be 3 time more sensitive than mine in NIR.
Stanislas-Jean


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Rick Woods
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Re: Ashen Light - Redux [Re: azure1961p]
      #5746852 - 03/21/13 03:03 AM

Quote:

there is no hiding place with a DMK DBK Flea3 Toucam or the like.




What on Earth makes you think that, Pete?


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stanislas-jean
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Re: Ashen Light - Redux [Re: Rick Woods]
      #5746894 - 03/21/13 04:54 AM

The question of ccd collection is a sensitive point for sure.
However considering the document brought by Buddy, I noted a ratio cresecent dark side of 10 000 (means 10 magnitude difference probably on the O3 colour channel).
This ratio would involve some exposure times for collecting something of 10 minuts.
Having done some trials with a sony 098BL chipset, beyond 30sec this becomes hard to not be annoyed by the light glare even with the occulting bar use of D3 density.
So from my opinion this should not be the subject on this forum to say
this is an illusion
this is lightning
this thermal
this is water vapor dissociation
etc...
but if each is existing which light level could be expected and therefore to discuss which capture method can be undertaken.
Frankly imaging is not only a fact to set a chipset and to practice exposures (this is the prior first step of a method in order to start an apraisal only).
The links brought by Buddy are interresting because some light levels are expected and this goes on this approach at final.
If somebody wants to pursiue on that approach, please goahead, I will follow with open mind in order to built some assessment methods that can be undertaken for the next Venus conjunctions.
Matter of a forum!
Stanislas-Jean


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azure1961p
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Re: Ashen Light - Redux [Re: stanislas-jean]
      #5746995 - 03/21/13 07:24 AM

Rick,

While there is greater dynamic range in vision, the ccd is ruthlessly effective in ferreting out details often invisible or close to invisible to the human eye. What it lacks in dynamic range which isnt much, it over compensates for in contrast boosting at levels no eye or brain can achieve. Add wavelet sharpening, saturation boosting and its pretty well drained the loche.

This same ability of the ccd to differentiate intensity, contrast and magnitude differences so well and beyond super human was well shown recently in a ccd image of Enceladus and Mimas beaming through the over exposed glare of Saturn. The differentian between Saturn and Mimas is well beyond 10 magnitudes Stan.

Pete


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stanislas-jean
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Re: Ashen Light - Redux [Re: azure1961p]
      #5747053 - 03/21/13 08:20 AM

We could discuss about this assessment. I saw such images also performed with a 10" and satelites of 0.18" disk, dark shadow and clear disk on planet, overexposed saturn disk and 11th magnitude stelite also but not closed to the planet for avoiding the glare of light.
Also the AL with ccd images null but no visual data at the same time, etc... images with 1Ám filter as well. This doesnot mean this is an illusion. It is needed more data and simultaneous data and numerous.
Keep in mind that it seems that Keck get light level on the dark side with the famous ratio of 10 000 in green/ O3 channel colour. This is a start.
But,
There is a proposal in my last post for something other than to get right. This is not interresting me.
And,
what is interresting is to built assessments as proposals for making after basis of observations and survey.
Stanislas-Jean


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azure1961p
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Re: Ashen Light - Redux [Re: stanislas-jean]
      #5747550 - 03/21/13 12:45 PM

Stan,

You seem to counter point for the sake of countering in itself. There is no way in heck you can see Mimas like that visually in any scope. And its fainter than 11v. Sometimes I think you enjoy the game of debate more than the substance of it.

Pete


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EJN
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Reged: 11/01/05

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Re: Ashen Light - Redux [Re: azure1961p]
      #5747637 - 03/21/13 01:24 PM Attachment (17 downloads)

This is my sketch of the crescent Venus. It should be considered definitive.

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stanislas-jean
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Re: Ashen Light - Redux [Re: azure1961p]
      #5747756 - 03/21/13 02:43 PM

Keep in mind that venus is observed in dawn light for the best and not on full night as for saturn.
Useless to stay here more time.
Stanislas_Jean


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stanislas-jean
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Re: Ashen Light - Redux [Re: EJN]
      #5747764 - 03/21/13 02:47 PM

EJN good sketch with cusp extensions, without doubt reason why this is smiling.
Stanislas-Jean


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GlennLeDrew
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Re: Ashen Light - Redux [Re: stanislas-jean]
      #5747835 - 03/21/13 03:21 PM

I'm inclined to doubt its reality. First, to have seen it in *daytime* means that it would have to be astonishingly obvious at night. The daytime sky is so very bright that in order to even begin to compete any extended source must necessarily be bright also.

If we take the daytime sky to have a surface brightness of, say, 2 magnitudes per square arcsecond, a source must be no fainter than 6 MPSAS if it is to be seen. This is about the same surface brightness as the sunlit surface of Neptune, which at night presents no difficulty at all, and moreover is more than sufficient to reveal color (the detection threshold of which is 18-19 MPSAS.)

In short, daytime observations of this phenomenon must certainly be illusory, for at night the effect would be glaringly obvious to all. And if the detection during the day is accepted as illusion, the possibility of its being so at night must be entertained.


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LivingNDixie
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Re: Ashen Light - Redux [Re: GlennLeDrew]
      #5747976 - 03/21/13 04:22 PM

Count me as a doubter. Has any spacecraft ever shown the light? I don't doubt people believe what they see, but that is not the same as the event or feature occurring

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Rick Woods
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Re: Ashen Light - Redux [Re: LivingNDixie]
      #5748345 - 03/21/13 07:20 PM

Well, though, it evidently only shows up once in a while. There may not have been a spacecraft looking when (if) it happened.
Tom Dobbins was a doubter until he saw it for himself, per a recent S&T article by him. I've seen airglow, lightning, aurora, and glowing-hot surface proposed as possible solutions. I don't really understand why one or more of these couldn't be the cause of the phenomenon.


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buddyjesus
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Re: Ashen Light - Redux [Re: Rick Woods]
      #5748477 - 03/21/13 08:37 PM

even though it is an aside, Mimas is visible visually, though I doubt as anything but a diffraction pattern.

Mimas was discovered by the astronomer William Herschel on 17 September 1789. He recorded his discovery as follows: "The great light of my forty-foot telescope was so useful that on the 17th of September, 1789, I remarked the seventh satellite, then situated at its greatest western elongation."[9]


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buddyjesus
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Re: Ashen Light - Redux [Re: buddyjesus]
      #5748488 - 03/21/13 08:46 PM

my opinion of ccds is that they aren't quite there yet. This is based on seeing raw and computer manipulated images from scopes twice as big as mine in diameter that rival my 4" scope in detail. The light they collect is just too blurred during even the short exposures that they select for stacking.

I subscribe to the ALPO Venus newsgroup on yahoo and haven't seen images shared since I joined of anyone trying to image the dark side. Most of their best images are in UV of cloud bands on the lit side. I highly recommend this group for the quality images and because the group isn't super active and won't flood your mailbox.

Another thing to consider is that ccd imagers usually use uv/ir cut filters as standard fare. The human ability for some people to see near UV light is documented, though I haven't found anything that says people can see near IR.


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Rick Woods
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Re: Ashen Light - Redux [Re: buddyjesus]
      #5748794 - 03/21/13 11:46 PM

Good post!

IIRC, in the other thread David Gray said he had unusually good eyesight in the near IR. (I could be remembering wrong.)

Whether or no, I'd never accept the results of a machine as a gauge of what is possible for a human. (At least, not a machine created by humans.)


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Edward E
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Re: Ashen Light - Redux [Re: Rick Woods]
      #5748844 - 03/22/13 12:07 AM

I do not think there has been a good showing of the event since the early 1980s. I have been looking but have not since it since my late 70s/early 80s observation. As Jack Horkheimer use to say "keep looking UP!"

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GlennLeDrew
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Re: Ashen Light - Redux [Re: buddyjesus]
      #5748851 - 03/22/13 12:15 AM

One can determine in advance the level of surface brightness Venus' night side much achieve, after considering such factors as the glare from the sunlit side, contrast-reducing light from twilight, airglow and zodiacal light, and atmospheric extinction. Taken together, these phenomena are not inconsiderable impediments to seeing any glow on Venus' night side.

The nature of the observations so far seems to me to practically dictate a planet-wide brightening, for the ashen light reports that I'm aware of are of an essentially uniform illumination of the entire visible portion of the night side. What phenomenon could be responsible?

Airglow in the upper atmosphere? It would necessarily be some orders of magnitude brighter than that surrounding Earth. And of course it would need to vary in intensity by a very considerable margin, in order to be not seen under otherwise optimal conditions and yet seen under awful conditions (i.e., daytime!).

Aurora? Could such surround the entire planet (or at least the entire night side?) That doesn't seem very feasible.

Lightning? The dense cloud would diffuse and attenuate any individual discharge to a very local glow. It would require to have essentially planet-wide discharge at high frequency and over relatively small separation to result in a continuous and uniform glow.

Sunlight scattering through the clouds and well into the night side? It doesn't happen on Earth, and so there is no reason to suppose it can do so on Venus.

One kicker for me is the fact that any such glow must compete with the very brilliantly sunlit cloud deck. In spite of the eye's huge dynamic range, the proximity of such an intense crescent in *immediate* proximity presents a source of scatter in both the optics and observer's eye.

In short, to be seen on Venus any night side glow would have to be rather more intense Earth's night side when moonlight is absent, and perhaps even with a bright moon illuminating it.


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azure1961p
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Re: Ashen Light - Redux [Re: Rick Woods]
      #5748858 - 03/22/13 12:22 AM

Quote:

Good post!

IIRC, in the other thread David Gray said he had unusually good eyesight in the near IR. (I could be remembering wrong.)

Whether or no, I'd never accept the results of a machine as a gauge of what is possible for a human. (At least, not a machine created by humans.)




But Rick that's not fair to the technology. Look at deepsky for example - even a lousy CCD will handedly outstrip the best visual and its not a slam at visual, just a case where technology has surpassed it. I think at the arc second level - on lunar and planetary - the human eye is still the best in terms of contrast and such but broader angular seperated features I think fall well into the hands of CCD. It's scary how well it does on Enckes even in medium apertures (large).

I'm primarily visual. I think I'm 10% imager so I'm not trying to justify my bent for the latter - its pretty tame. But the evidence in even a 4" refractor on Jupiter is crazy good.

Doublestars though just aren't there yet in CCD. They need a lot more sensitivety for diffraction patterns in size and brightness difficulties.
Pete

Edited by azure1961p (03/22/13 12:24 AM)


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