Why does Venus appear to change direction during its transit across the sun?

[waynet]

I took a look at this video of the transit:

http://anon.nasa-global.speedera.net/anon.nasa-global/venus_transit/UV1600_eastlimb2.mov

And something just doesn't look right. It appears that Venus changes direction once it comes into full view. I played it foward and backwards, put a straght edge on it and it does seem to deviate.

Can anybody explain why it looks like that?

 

[enigma]

Rotation of the Earth during the transit changes the angle of the Sun's north pole as viewed from the telescope, maybe?

 

[farIR]

Oh, man, that's bizarre.

I took a movie of the thing too - think I'll have to go back and review it, but I really don't think I noticed anything like that.

Did you get footage as venus crossed the opposite limb? I'd be curious to know if this is observational effect which is observed when it's near the sun's limb, much like the mysterious "tadpole" effect (ohterwise known as the "black drop" effect).

What did you take the footage with? - I had a 14inch schmidt-cass and a sony 5 megapixel and my video isn't nearly as good as yours.

 

[AD]

I don't think the field rotation is significant in this clip.

 

[AD]

Over on another forum, someone posted this image of the transit from TRACE:

http://vestige.lmsal.com/TRACE/transits/venus_2004/images/VenusTransit2004_1600small.gif

The apparent 'bobbing' motion of venus is the effect of parallax due to the satellite's orbit about the earth.

What is the source of the clip on this page?

 

[farIR]

^oohhh, yes that would make sense now wouldn't it? :P

 

[waynet]

Yes that would make sense if that clip came from a satellite. I found that clip from this page:
http://www.nasa.gov/multimedia/imagegallery/image_feature_184.html

 

[AD]

Then it came from TRACE.