Quote:The ashen light of Venus is an optical illusion created by the eye/brain filling in an area the cusps of a crescent infer should be there.Pete
Mardi 4" achromat, ETX-70, 8"cat. Whitepeak Lunar Observatory Website
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Quote:Quote:The ashen light of Venus is an optical illusion created by the eye/brain filling in an area the cusps of a crescent infer should be there.Pete That is *one* theory.... Others, more likely IMO, are 1)static electrical discharges in the atmosphere (lightning), 2)phenom similar to earth auroras 3)a glow producing reaction of UV with CO2 molecules. And 4---an as yet unknown mechanism. Although the eye can play it's share of tricks, it is, I believe, unwise to assign observer imagination as a most likely cause by default when something unusual is observed. Doing so was once de rigueur but I think this default has gained needed nuance since, considering the 'spokes of Saturn's rings' (once declared imaginary, now known as real) or *some* lunar TLP varieties (flashes), again once dismissed as imaginary but now recognized as meteor strikes. ETC.
Cactus Patch Observatory / 14" LX200
"The four points of the compass be logic, knowledge, wisdom, and the unknown. Some do bow in that final direction. Others advance upon it. To bow before the one is to lose sight of the three."
Quote:The fact that absurdly small refractors had shown this effect while a 60" didn't and other peculiar discrepancies only go to support the fact that its an eye brain illusion. Sure there's theories a plenty but its all pretty thin . Not that these phenomena don't exist, but that they are seen visually is an impossibility.Back in the 80s maybe, or early 90s Sky and Tel had a revealing article on the quantification of ashen light accounts that often defied expectations for when it should have shown in great scopes but instead revealed in small aperture. I couldn't think of a bigger myth in contemporary visual astronomy . Modern CCD imaging has infact done this and their is no wiggle room for visual sighting justification . The retina simply isn't sensitive to infrared.That this Ashen myth persists is peculiar. Again, is there atmospheric activity and so on - absolutely -I have little doubt. But I have full confidence no human being as ever or will ever see this *light*.Pete
Quote:Ok, first, that is exactly the same argument used to "disprove" the reality of "spokes" in Saturn's rings.----Actually its not the same argument at all. The best observers with large aperture saw these features. This is in line with a real phenomena as opposed to saying Steve Omeara saw the spikes with an 3" refractor while Clyde Tombaugh failed with a 16". It's not true of course Clyde did infact see it with the 16 and Omears with great aperture/scope which threshold observations dictate.-----Second,-----That your counting here is humorous but ill move with the step...------ "thin" doesn't translate to "impossible"...rather it translates to "not fully understood" and or "improbable".--------And since there are no absolutes in life so goes this hiding space for erroneous observation to call a home.----Third, 80's and 90's? Things change and those who make declarations of certainty risk eating crow--especially in planetary science (which includes the Moon). -------No crow here snd that it made the magazine is testament to not only its historic rekevance but persistence of illusion though in fairness to sky, they were more liberal in interpretation (pre CCD too so...)------Take Venusian lightning for example... In the late 90's, based on Cassini data on it's flyby of Venus on it's way to Saturn, a team led by Gurnett of the U of Iowa concluded "If lightning exists in the Venusian atmosphere," the team concludes, "it is either extremely rare or very different from terrestrial lightning." But...lol...more recently we have this from Nasa: "In addition to all the pressure and heat, we can confirm there is lightning on Venus -- maybe even more activity than there is here on Earth," said Christopher Russell, a NASA-sponsored scientist on Venus Express. In the same report (2007) they declared this lightning "unique from Earth" because there was no water vapor involved...except now there apparently *is* (ESA et al findings since).------/Interesting but doesn't apply to what's reported visually. Visual reports offer no flashing fluctuations but more over its be highly unlikely an entire hemisphere is experiencing a simulataneous lightning storm of unwavering voltage with the steadiness if a fluorescent light however dim.Does it have lightning? Ill bet it does. Not full time globally fluorescing with bolts of uniform output.-------Fourth, have CCD's yet caught the spokes in Saturn's rings? I forget, but am curious...------ CCDs like even the one I own have routinely recorded the spokes. Always, no but several times per apparition.Usually with 14" sperure and larger . Why the folks here on CN even have made little animates showing the arcs whopping around on the ring structure. Believe me Mardi - I'd ANYONE can see it visually than the CCD ought to handedly acquire it as well. Infrared doesn't count.---/----Fifth------/More counting????????-------/, the phenom remains "controversial" because of an extensive observational record and a generalized lack of professional scientific interest in resolving what is really a purely observational controversy. *But* what the "ashen light" issue has done for Venusian science is neatly summarized by Lisa Riley: "There have been many questions as to the relevance of any findings regarding Venus' ashen light. Many argue that it offers no known practical applications. But, scientists conclude that continued research is interesting for its own sake, at least partly because it explains an old astronomical mystery. By observing the motion of glowing air in the Venusian atmosphere, scientists can better understand the dynamics of that atmosphere, and those observations might shed light on the dynamics of Earth's atmosphere. Moreover, scientists hope to refine observing techniques used to study this atmospheric phenomenon to assist in future studies of other planets that orbit distant stars. As such, the scientific exploration of Venus' "ashen light" will continue."-------Mardi / the loche is empty - there's no monster./--------Anyway, you could well be right...may well be an illusion and a myth after all. ---------AaaaaahhhhhhBut I am not predisposed, *personally* to slam doors ------its not slammed . its slightly ajar pending real supporting data in vidusl wavelengrhs.------shut on any phenom when the current state of research of this planet's atmosphere is in such a dynamic phase --and as it presently promises to remain for some time...BTW, while I was browsing around the net looking into this, i found a number of references in the (scientific) literature of "ashen light" referring to *earthshine" of the Moon. So, it may not be as plainly incorrect of a usage of that term as it appeared at first blush.
Geoff... --Nexstar 8SE + bits and pieces-- ================================== ...Think before you act... -----------------------------