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Subject Calculating redshifts and blueshifts ~ A "How-To" site
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Original Message Found this interactive site and wanted to share...I had a dream last night about measuring redshift/blueshift. Of course I forget 'how' once I woke up so I went looking to figure out how to calculate redshifts on my own.

Sloan Digital Sky Survey/SkyServer

This page shows you how to actually calculate redshifts, but the previous page will show you how to look up redshifts of twelve galaxies.

SNIPPET

Astronomers learn an amazing number of things from analyzing spectra. In this section, you will focus on just one application: you will learn how to measure the redshift of a galaxy from its spectrum, and you will learn how to interpret and use the redshift.

Measuring Redshifts

Measuring a redshift or blueshift requires four steps:

1) find the spectrum of something (usually a galaxy) that shows spectral lines

2) from the pattern of lines, identify which line was created by which atom, ion, or molecule

3) measure the shift of any one of those lines with respect to its expected wavelength, as measured in a laboratory on Earth

4) use a formula that relates the observed shift to the object's velocity.

An example will help to show how this works. All spectral lines are created when electrons move around inside atoms. Hydrogen is the most common element in the universe, and it is often seen in galaxies. The spectrum of a hydrogen-containing region shows a pattern of spectral lines called the "Balmer series." The Balmer series is easy to reproduce in a classroom with a hydrogen discharge tube. The force that makes the gas glow is not the same as in galaxies, but the spectrum - the pattern of lines - is the same. Either from your own measurements in the classroom, or by looking the Balmer series up in a table, you know the rest wavelengths of Hydrogen's spectral lines to be as follows: (The wavelengths are given in Angstroms, equal to 100 trillionths of a meter)

And here is a PDF titled: The redshift and geometrical aspect of photons

I found it interesting that the author speaks about the possible redshift effect of dark matter field fluid. I'm only a few pages in so far...