Quote:
Originally Posted by l3gendluk3
Unfortunately my research project involves measuring the red shift/blue shift of the sun so I would need a direct view on the edges. I could bump up the exposure as my mount could easily handle it although its not going to be a full spectra, I will be selecting 3 or 4 samples lines and measuring the difference between those and lab samples.
The sample spectra would be great as it could give me a look on where the lines are supposed to be.
Thanks,
Luke
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Hi Luke,
an interesting project
Have you checked the wavelength shift you are trying to measure ? A back of envelope calculation suggests the Doppler shift from solar limb to limb will be tough to detect using the SGS. Even with the higher resolution LHIRES a measurement would be marginal.
If you do decide to go ahead, I suggest placing the slit horizontally along the equator so you can measure the velocity profile across the width in one go. This allows differential messurements to be made which gets round the problem of stability between measurements which will be poor with solar measurements due to temperature effects and the need to use a lab lamp reference.
See here for a similar measurement on Saturn and Jupiter. The shifts for the sun will be significantly smaller though
http://www.shelyak.com/dossier.php?id_dossier=16
To measure the very small shift I would recommend using cross correlation of the whole spectrum rather than measuring individual lines. You will be able to detect smaller shifts this way. You will still need to use the lamp spectrum to define and correct for any inherent slant/curvature in the lines.
Cheers
Robin