Given that I can see light from stars with my naked eye. And also some lenses suffer chromatic aberration.

I would think that with enough training I could simply hold up a lens to a star and look at the colours refracted through it into my eye and be able to tell the red-shift of the star.

Thus with a simple piece of glass I would be able to observe how fast a star is moving away from me.

Do you think this is a realistic prospect?

  • $\begingroup$ Have you ever observed absorption lines in daylight? In principle, a pocket spectroscope will do. It is safest to look at clouds. $\endgroup$ – user137289 Feb 11 '19 at 0:15

To try something like this with any chance of success, you'd be better off using a prism instead of a lens, because a prism is designed to split light into an easily-studied spectrum of different wavelengths.

Since the light from a given star is pretty faint, the thing to do would be to mount the prism in a telescope; this will also let you aim it at one star at a time.

What you will find is that splitting the light from a single star with a prism yields a spectrum too faint for your eye, which is why the guys who did this experiment may years ago used a camera with sensitive film in it and long exposure times instead of their eyes to collect the spectra taken through telescopes.

With a high-grade telescope and ultra-sensitive film you can discern the absorption lines and their displacement relative to the background spectrum of a distant object, and deduce its velocity along the line of sight; this can't be done by eye.


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