OSETI might want to monitor the "Venus Transit" and record those "Unnatural Ashen Lights".

Venus; ashen light as an extremely faint glow occasionally observed on the dark side of Venus, was first reported by Riccioli in 1643. The term "ashen light" is however somewhat bogus, in that earthshine is hardly perceptible to the astronomy eye, as it takes the most recent of CCD and the likes of KECK-II optics as to actually detect such earthshine (ashen light) upon the nighttime season of Venus.

Ever since 1643 (360 years and counting), it seems as though nearly all natural forms of such illumination have been ruled out, at least for the past 360 years and counting there's not been a viable natural alternative to those illumination spots such as recorded by the BAA as being other than artificially generated. Besides the BAA recorded images of illuminations (on the daylight side none the less), here's another more recent sighting as follows;

http://www.irishastronomy.org/boards (oops; it looks like I inadvertently broke this site, either that or one of their godfathers such as "Brian O'Halloran" pulled the plug after I'd suggested upon other life existing on Venus, plus a little something other pertaining to photons at rest.

Topic: Venus 'Ashen Light' seen! by; Dave Lillis
"I'm really starting to doubt myself here,!!!!
What I saw DID look like it had a very dark purple hue to it !!!!
The time I saw it was at 22.20, the sky was fairly dark at that stage., I have images of the planet at this stage through my 12" using the webcam, and I noticed no trace at the time of any illumination to hint at ashen lights, but then again I wasnt looking for it as I convinced myself that it was an "eye" illusion."

My reply to the above (before the plug was pulled);
That reported "very dark purple hue" is perhaps the 425 nm spectrum that's best suited at taking advantage of the opacity of them acidic clouds, and that's a fact. At least of anything below 450 nm isn't all that much in competition with earthshine.

Utilizing a band-pass filter of 400~450 nm should offer the most photon bang for the buck/euro, although a more specific filter should only improve upon those observations, and of a recording whatever might be encoded within that spectrum of photons might become even a little more interesting, to say the least.

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However folks, expecting any of these pretentious (NASA moderated) astronomy types to place their warm and fuzzy stamp of approval upon the notion that Venus could have been harboring other life NOT as we know it, apparently this notion isn't a viable option, though as for their having humanity wasting more decades and trillions of dollars is oddly worth every penny, especially if those pennies are going into their institution or better yet into their own pocket, meanwhile the polluting of mother Earth and of the pillaging for extracting energy resources to a fairlywell, along with all of the collateral carnage, is just fine and dandy.

God forbid that we should consider upon the obvious prospects or perhaps fact of the matter that Venus isn't quite so darn hot and nasty, nor insisting that of sufficiently smart folks couldn't have managed to have coexisted in spite of our arrogance, greed and utter stupidity.

Ashen lights of Venus have been simply too well noticed, and of various radio astronomy and by way of numerous other instruments (other than visible photon detections) have not sufficiently established upon any sufficient natural source as for their existence. That's sort of physics duh-101 for those illumination spots being of pure photons which thereby obviously had to have been created from the surface or perhaps from aboard some high flying rigid airship, cruising quite safely and calm just below those nasty clouds.

As for considering my rigid airship notion; as for such technology providing a suitable astronomy platform by which to safely operate on Venus at perhaps 25+km shouldn't be ruled out. Even the notion of such rigid airships being entirely capable of their cruising above them relatively cool nighttime clouds isn't outside the box of accepted physics-101, as their nighttime upper cloud level might at times fall to below 50 km, whereas a 60+km cruising altitude is possible.

BTW; I have another page or two to offer, but I do need and would certainly appreciate your input:
http://guthvenus.tripod.com/illunination-spots-02.htm
http://guthvenus.tripod.com/illumination-spots.htm
http://guthvenus.tripod.com/earthshine-moonshine.htm
http://guthvenus.tripod.com/gv-illumination.htm
http://guthvenus.tripod.com/gv-hot-spots.htm