Stargazing Stellar abberation (water in telescope)

[Buckethead]

I've been reading about stellar aberration and was particularly drawn to the experiment where two telescopes are tracking a star but one is filled with water to slow the speed of light down. The results of the experiment show both telescopes to be tilted to exactly the same angle which contradicts logic. This is explained somewhat in wiki as a byproduct of length contraction. I don't understand how length contraction can fix this. Can someone help out? Thanks.

 

[davenn]

have you got some references for that please ?

never heard of a telescope filled with water

 

[Buckethead]

From Wikipedia "Stellar Aberration"

"However, it soon became clear Young's theory could not account for aberration when materials with a non-vacuum index of refraction were present. An important example is of a telescope filled with water. The velocity of the light in such a telescope will be slower than in vacuum, and is given by

rather than

where

is the index of refraction of the water. Thus, by Bradley and Young's reasoning the aberration angle is given by

[PLAIN]https://upload.wikimedia.org/math/4/5/3/453fb5ca1793c35cb0666e886fad9665.png.
which predicts a medium-dependent angle of aberration. When refraction at the telescope's objective is taken into account this result deviates even more from the vacuum result. In 1810 François Arago performed a similar experiment and found that the aberration was unaffected by the medium in the telescope, providing solid evidence against Young's theory. This experiment was subsequently verified by many others in the following decades, most accurately by Airy in 1871, with the same result.[14]"