Hi All.
Was surfing the net when I can across this interesting article. Please read it.
http://skyandtelescope.com/news/article_1277_1.asp
During venus transit how many of you have actually seen the blackdrop? Looks like the resolving power of the scope is very important. I saw what seems like a black drop through a handheld DV through my sch's C8. I hope you can share what you saw or taken on the day of venus transit.
Black Drop Or Not?
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kcy
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Black Drop Or Not?
Yours Sincerly,
Kong Chong Yew 8)
SP astronomers
Kong Chong Yew 8)
SP astronomers
Wonder who this Jospeh Tey guy is.. maybe should invite him to Singastro. Weixing or ChaoKnight should have sent their pictures to be printed instead. 
Anyway, I took a webcam movie of the whole contact II, and it turns out that while the black drop effect is definitely noticable, it is the resolving power of the telescope combined with turbulence that produces it.
For example, in this sequence, I picked the frames least affected by turbulence, and the black drop effect is barely noticable.
In most of the other frames, the turbulence causes the edges to take on rounded shapes. For example: http://www.singastro.org/album_pic.php?pic_id=230
Therefore, it seems to me that the clear moments are so few and far between that we observe a consistent black drop effect.
Chris
Anyway, I took a webcam movie of the whole contact II, and it turns out that while the black drop effect is definitely noticable, it is the resolving power of the telescope combined with turbulence that produces it.
For example, in this sequence, I picked the frames least affected by turbulence, and the black drop effect is barely noticable.
In most of the other frames, the turbulence causes the edges to take on rounded shapes. For example: http://www.singastro.org/album_pic.php?pic_id=230
Therefore, it seems to me that the clear moments are so few and far between that we observe a consistent black drop effect.
Chris