Doppler shift & spectra..

[NickK]

How do you folks see/deal with doppler shifts?

[ronin]

Without knowing I suspect that it is relatively small until you start getting spectra of distant objects like galaxies.

Would have thought that anything within the Milky Way was not approaching or receeding that fast to make a significant impact on the results. Some impact if the equipment was sensative enough but not in the order of red shift that distant galaxies demonstrate.

[robin_astro]

Hi Nick,

Measuring Doppler shifts is an important tool for spectroscopists

It is possible,  using amateur equipment, to measure Doppler shifts over a very wide range of velocities from a few tens of km/sec (eg the wobble of a star due to exoplanets)

http://www.astrosurf.com/buil/tauboo/exoplanet.htm

to redshifts up to 4  (though this is due to cosmological expansion rather than a true Doppler shift. )

http://www.threehillsobservatory.co.uk/astro/spectra_22.htm

and everything in between

eg the expansion rate of a supernova explosion

http://www.threehillsobservatory.co.uk/astro/spectra_6.htm

or the rotation of a Galaxy

http://www.astrosurf.com/buil/forum/ngc7331_poster.png

Changes in the shape of a spectral line due to doppler shifts can also be used by amateurs to probe the way an object is moving internally eg

http://www.threehillsobservatory.co.uk/astro/spectra_40.htm

Within our own galaxy, Doppler shifts of stars due to their radial velocity relative to us are typically a few tens of km/s up to a few 100 km/s at most  (100km/s = 2 Angstrom shift)

The  shift of a given spectral  line is measured relative to a standard, eg either a calibration lamp or relative to a known radial velocity standard star.  When looking for accuracies better than a few  tens of km/sec then the rotation of the earth and velocity of the earth round the sun has to be taken into account.  

Cheers

Robin 

[robin_astro]

It is possible,  using amateur equipment, to measure Doppler shifts over a very wide range of velocities from a few tens of km/sec (eg the wobble of a star due to exoplanets)

http://www.astrosurf.com/buil/tauboo/exoplanet.htm

That should of course have read a few tens of metres/second not km/sec  - a remarkable achievement by Christian Buil and colleagues

Robin