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azure1961p
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Re: Ashen Light - Redux new [Re: stanislas-jean]
      #5761808 - 03/28/13 07:04 AM

No Stan it's you as usual dismissing facts because it isn't convenient to your posturing - if you had actually read the thread and followed the link its s little more conclusive than that. While it can be argued these are infact stills and a night time event could've occurred unbeknownst to the imagers this casual "click clack" swipe at some of the best imagers out there debases your own credibility. At least read the thread before you slam it.

Pete


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stanislas-jean
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Re: Ashen Light - Redux new [Re: azure1961p]
      #5761892 - 03/28/13 08:11 AM

Is it a reference, surely not.
What is a qualified method for acquisition?
Stanislas-Jean


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azure1961p
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Re: Ashen Light - Redux new [Re: stanislas-jean]
      #5761960 - 03/28/13 09:14 AM

Some things can't be explained away with simple translator miscommunication and this one of them. Your question has already been addressed in the previous post.

If you are looking for a Kodak camera and one going click clack then this is all very pointless.

Pete


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buddyjesus
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Re: Ashen Light - Redux new [Re: azure1961p]
      #5762166 - 03/28/13 10:52 AM

I thought the photos were beautiful. I was surprised to see details in the images for the dark half at all. Not quite definitive but good data. Would be definitive I think if photos taken while others confirm that they see the AL taking place.

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GlennLeDrew
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Re: Ashen Light - Redux new [Re: azure1961p]
      #5762185 - 03/28/13 11:02 AM

Pete,
What Stanislas-Jean is getting at is that the images in that other thread are more optimized for the day side. In such case, the exposure will not properly pick up the much feebler glow of the night side and surrounding sky; these dim signals will be well lost in the noise. Longer exposures, which vastly blow out the day side into complete saturation. The images we've seen probably had typical exposures of order 1/100 second, whereas exposures of several seconds are required. In this way the much weaker signals can be brought well enough above the noise floor and measurements for any night side limb contrast undertaken.


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stanislas-jean
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Re: Ashen Light - Redux new [Re: GlennLeDrew]
      #5762230 - 03/28/13 11:33 AM

Thanks Glenn.
The question is actually: what is a qualified procedure?
This a procedure that perform photometry assessments for the present case.
We try to determine the lights level that can involve a trace of the chipset: on the planet and in parallel on cible with known light levels.
Because the light level intensity is depending on the color channel and is disturbed by the light glare, mainly, the chipset has his own sensitivity to colour channels.
It's a problem regarding photometry measurements.
A kind of calibration method in fact. Had it been performed?
Answer is no.
Stanislas-Jean


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azure1961p
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Re: Ashen Light - Redux new [Re: stanislas-jean]
      #5762276 - 03/28/13 12:05 PM

John Boudreau hadentioned that exposures overexposing the Venus image still yielded no night side illumination and infact was the same black as the surrounding dark sky value.

My objection with Stan is his cavalier dismissal of the technology at hand and the talented individuals using it.

I'm a primarily visual observer. I dabble in imaging . I don't believe visual observing will ever fall out of favor as a rewarding pursuit . CCD is a great supportive tool to the endeavor.

Stan, the idea of the light level disturbing the chipset and other notions are unfounded. The diversionary contortions you go through to float a belief is astounding. These loopholes, conditional bypasses, faints, jukes and evasive maneuvering and what have you is beyond tedious.

Pete

Edited by azure1961p (03/28/13 01:14 PM)


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stanislas-jean
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Re: Ashen Light - Redux new [Re: azure1961p]
      #5762497 - 03/28/13 02:23 PM

So we note.
But this is not a demonstration and a photometry measurement.
We donot know until which light level he was reaching on dark side (even with no result because this corresponding to a threeshold, not quantified and not calibrated).
Do you understand?
At final the light glare is a main disturbing point.
Perform trials you will see.
Do you remember forums for uranus and the no possibility of capturing the banding system: go to my report about, a below forum here you will have images about since july 2012 visual channels, OK.
Stanislas-Jean


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azure1961p
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Re: Ashen Light - Redux new [Re: stanislas-jean]
      #5762621 - 03/28/13 03:48 PM

Ok here's where I opt out of the thread.

Cheers.

Pete


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GlennLeDrew
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Re: Ashen Light - Redux new [Re: azure1961p]
      #5763032 - 03/28/13 07:29 PM

One need not necessarily calibrate. The first task is to attempt to detect the night side's limb. For then even if the glare from the day side is strong, hopefully there is still sufficient contrast to trace the circular edge of the night side. If at least some segment of the dark limb is detected, and it lies where expected (as the continuation of the day side limb), one has made a pretty firm observation.

Taking into account, of course, a flipped ghost reflection of the sunlit crescent which by chance could line up very closely with the dark limb.

Naturally, all measures to block or attenuate the glare of the sunlit crescent can only help. Veiling glare can seriously reduce contrast. In any event, the exposure time must be sufficient to bring the sky glow at least a few sigma above instrumental noise, so as to afford a reasonable signal for the detection of the dark limb's edge.


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Rick Woods
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Re: Ashen Light - Redux new [Re: GlennLeDrew]
      #5763196 - 03/28/13 09:11 PM

There's always the possibility that the phenomenon was simply not occurring at the time the images were taken. Remember, it's only seen occasionally.

This is the same beef I have with the Martian Blue Clearing: no definitive observations are ever made at the same time the clearing is being reported telescopically. No HST, orbiter, etc. data is gathered to compare notes and try to solve the problem. It's strange; amateur observations are used frequently to support and supplement space probe observations; but the reverse never occurs. When an amateur observation could really use the input from a space-based observation location, it's never made available.


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GlennLeDrew
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Re: Ashen Light - Redux new [Re: Rick Woods]
      #5763352 - 03/28/13 10:50 PM

Has anyone compiled data in order to obtain some estimate of the ashen light's frequency? The lower the frequency, the more likely it must be due to some 'uncommon' phenomenon.

For example, if light reflected from Earth were to be the source, it must be seen at every apparition within some range of phase angle and when the planet is seen in a sufficiently dark sky. The range of brightness of Earth as seen from Venus, within the required range of phase angle, cannot be so large as to result in the AL 'switching' between readily seen and not seen. After all, Earthshine on the Moon at given phase varies not enough from one apparition to another to be at all apparent with any certainty. I should think Earth's albedo, considering extremes for the range of cloud/snow cover, varies by perhaps 50%, or 0.5 magnitude. Even a factor of two variance is 0.75 magnitude. This is not terribly significant.

If the observations of the AL are not sufficiently consistent in frequency when conditions would otherwise be favorable, I think it fairly safe to discount Earthshine as the cause of the AL. From nothing more than a statistical analysis, let alone the not inconsiderable faintness of Earthlight at Venus, and the difficulties imposed by considerations of contrast.

So, what other conceivable phenomena can cause a visibly detectable glow (necessarily at least in part within the visual spectral band), the surface brightness of which must compete with the dazzling sunlit crescent and other wreckers of contrast?


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buddyjesus
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Re: Ashen Light - Redux new [Re: GlennLeDrew]
      #5763503 - 03/29/13 01:15 AM

I would like to see the imagers try to block out the lit side some. couldn't hurt. Am I the only one who saw the dark side on some of the photos? even surface detail from the IR? That should be proof of the dark side images coming out with something, even if not AL.

i also agree, the phenomenon might not have been active during those photos. Considering there are AP people who do constant dark side moon monitoring for impacts, it wouldn't take much for someone to do an actual monitoring program with a webcam at least. Actually it would probably take two imagers at different sites to catch something simultaneously for definitive positive proof.


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stanislas-jean
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Re: Ashen Light - Redux new [Re: buddyjesus]
      #5763585 - 03/29/13 03:10 AM

That's not enough but in the good way.
I insist that for making pertinent comparison photometry calibration is needed.
Because if the results on dark are negative, this means only the fact that a certain amount of light cannnot be and never be captured. A little above this value a certain trace on the image may commence to appear. From an observer to another, this light level, a threeshold, is not the same, not for a few but greatly (can go up 100x).
This threeshold well determined is an excellent indicator because we know where we are, even with negative results.
The AL if existing may be just under this level, this is a possibility.
According to long distance test the ratio of 100000 (near to for crescent/dark side)) remains visually accessible (this imply more or less a light level of 0.05cd/m2 on dark side).
Now with a 098BL chipset the exposure needs to be great sothat it is difficult to catch consistently something but we are not so far from this target.
So a step more in possibility is to be find. I am in a ratio of 10-100 of uncertainty between visual ability and imaging ability. The distance between the 2 means that I tried to evaluate. This is not accurate but a trial to fix the status, with a luxmeter how it is and the test method in use.

For the collection of AL data since decades, I know the BAA that does this job, Alpo may does also. The problem is the episodic collection of observations for each observer. Is the collection of several observers of unequal ability and conditions can do a representative status? This may be under question. Pesonally I didn't see all these data for having an accurate view about.

Buddy, you say you have data with light collection on the dark side. I am interrested in.
Could issue some of them here with the conditions in use?
This would be interrested to see for the discussion.
Stanislas-Jean


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buddyjesus
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Re: Ashen Light - Redux new [Re: stanislas-jean]
      #5763598 - 03/29/13 03:41 AM

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/5758956/page...

i clicked every link that was put up so it is in this thread or one mentioned.


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stanislas-jean
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Re: Ashen Light - Redux new [Re: buddyjesus]
      #5763617 - 03/29/13 04:19 AM

Thanks Buddy.
In fact I saw these posts in past.
I noted the fact that in the range of 850-1000nm the images captured corresponded to deep clouds of the venusian atmosphere.
Most of the pictures given are for the crescent and some performed in NIR with 2 filters the 1000nm and the omega 956nm. The omega filter get clearer views with around 1s exposure more or less at F10.
I think the exposure pushed 10 or 100x more may occult the images even with the occulting bar in deep red channel. Now the observer may comment his work about, more than me.
These works pre-suppose the fact that nothing is existing in visual fields and this is not demonstrated in fact through these results for the reasons given in the last post.
AL may not exist but here this is not completed enough.
Matter of light levels expected to be catched.
Stanislas-Jean


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buddyjesus
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Re: Ashen Light - Redux new [Re: stanislas-jean]
      #5765055 - 03/29/13 03:45 PM Attachment (6 downloads)

this one from wayneJ is the one i saw the unlit side. it is in the thread I posted above. my imagination?

Edited by buddyjesus (03/29/13 06:17 PM)


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azure1961p
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Re: Ashen Light - Redux new [Re: buddyjesus]
      #5765427 - 03/29/13 06:01 PM

Quote:

this one from wayneJ is the one i saw the unlit side. it is in the thread I posted above. my imagination?




That's correct.

Pete


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buddyjesus
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Re: Ashen Light - Redux new [Re: azure1961p]
      #5765478 - 03/29/13 06:20 PM

when i cover the bright portion, the dark side does darken(prolly to a moot level)but was still easily visible in the image to myself and bro. my guess is this was from the IR portion, but just guessing.

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azure1961p
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Re: Ashen Light - Redux new [Re: buddyjesus]
      #5765754 - 03/29/13 09:20 PM

Ah correction to my affirmation - it is showing after all!. I'd guess the wavelength is responsible. Wayne would have the info on that as Im sure John B or Sean W might.

Pete


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