First attempt at spectroscopy: Sirius and Betelgeuse

[SkyViking]

Hi everybody, tonight I tried a first attempt at spectroscopy :D
I had an old diffraction grating lying around (marked as 7500/inch) which I taped to the front of my Canon S5IS. I then mounted it on top of my scope with the tracking turned on, fully zoomed in, and successfully recorded the spectra of a couple of bright stars. Very exciting :)

There were immediately some obvious lines visible for both Sirius and Betelgeuse, so I loaded the raw shots into photoshop and cropped carefully around the spectra. I then resized vertically to 1 pixel to get the average value for each wavelength (I assume this will somewhat combat any noise in the image), and then I resized again to make the spectrum nice and broad.

I have attached the result as a comparison between the spectra of Sirius and Betelgeuse. It definitely shows something similar to what I would expect, but maybe some of you with more experience can tell me how much of this data is just noise? I suspect all the tiny lines are noise, but there is a lot going on especially in the Betegeuse spectrum which seems real enough to me. Are there perhaps reference spectra somewhere to compare with?

With regards,
Rolf

[sheeny]

G'Day Rolf. Great start!

There's lots of reference spectra around, but you might need a program like VSpec to view them, however, search this forum and I'm sure you'll find spectra of both Betelgeuse and Sirius in JPG format for comparison. I'm sure I've posted spectra of both of these and so have others probably.:)

A couple of free programs I suggest you get so can process them and keep developing are IRIS, and VSpec.:thumbsup:

You can hten cut down the noise by stacking multiple images, preprocess them in Iris and convert them to graphs and analyse them with VSpec.

Welcome aboard!:D

Al.

[Merlin66]

Rolf,
Good start.
The dark lines in the Sirius spectrum are due to Hydrogen; the darker bands in the Betelgeuse are due to TiO molecules.
Richard Walker has recently published on his website a very good annotated Spectral Atlas which would help you.
http://www.ursusmajor.ch/downloads/spectroscopic-atlas-1_3-english.pdf

[SkyViking]

Thanks guys, that was very informative and helpful! And that PDF seems to be a goldmine :) I'll wait for the clouds to part and see if I can get better results next time by stacking lots of frames.