After help understanding black drop effect

[aussieskywatch]

Good evening every one, first post in this forum and only an amateur astronomer here so please be kind.
My question relates to the observable black drop effect, when watching the transit of Venus, at first when i looked up what might cause this effect the answer seamed to simply to be poor optical equipment that was to blame, however i believer the black drop effect has been witnessed in more recent times with some of the more high tech observing tools available to us, including from outer space where local atmosphere could be ruled out as a contributing factor.
The other reason i am inclined to disbelieve that atmosphere is a large contributing factor is that the black drop is also witnessed during a transit or mercury, a planet as i am lead to understand, that has little to no atmosphere.
Here is where I'm asking fro the forums help
1) Does a black drop effect take place during an annular eclipse?
2) Does anyone know of and combined efforts to image the last transit of Venus in varied wavelengths using different pieces of equipment that were set to image at the same time or of multi-spectrum imaging systems that could process different wavelengths at the same time through the same piece of equipment?
3) the reason for my question is to investigate if gravity bends light, which it is already known to do, but at varied rates for different wavelengths of the light spectrum?

Looking forward to any responses that might help me understand this a little bit more

 

[mathman]

http://en.wikipedia.org/wiki/Black_drop_effect

Try the above.

 

[aussieskywatch]

That link was where i got most of my current understanding from mathman, still quite limited on answers and doesn't really help as much as I was hoping it would.
thank you for your help though