Spectroscopy

Hello,

I have acquired a 1000 traits / mm diffraction grating which I stuck on a clear lens filter. I use it with a 70-200mm Sigma and a 11-16 Tokina. The setup is as seen below.

The resolution seems quite good - the sample below is taken with the Tokina. At longer focals it increases quite dramatically.

Would you know some software that would take such photos and calibrate them? (IRIS is way too crazy for me).

The final aim would be to adapt this to the astro setup.

What did you use as the light source in this pic. Very cool by the way. I think you could use a scope and get light from bright stars like Vega, Arcturus and such and get neat results

Source was a mercury-sodium street lamp. I've played around with quite a few different sources and results were unexpectedly good - I shall thus persevere.

I've found that not only do you have emission / absorption lines, but the brightness of those lines vary greatly. The dynamic range is quite large and one needs to expose accordingly.

See if this is too basic for you or if it is useful.

LINK

iphone is used to take picture and app is SpectraSnapp - LINK

samsen wrote in post #16349534
See if this is too basic for you or if it is useful.

LINK

iphone is used to take picture and app is SpectraSnapp - LINK

After watching this video I now know what Apple users use to (not so much now I'm guessing) feel like, living in a world dominated by X86 software.
What is my point, the spectra scope being made in the video requires an Iphone!

Hello,

Thank you for the links - interesting application. So much more so as I've recently purchased a mac, which makes me feel very lonely, astro-software speaking.

I think the tool you're looking for is VSpec (unless you've gone completely Mac).
There's also ISIS which is from the same stable as IRIS so may not be to your taste.
I'd recommend either or both of Ken Harrisons books and he frequents a few forums. He's very enthusiastic about getting people into spectroscopy and very helpful.

Oh yes, that's *precisely* what I was looking for. Thank you ! I'll come back with results.

Unfortunately I bumped the focus but I took this at the solar eclipse last year using the same technique as your shot above.
Just at the start and end of a solar eclipse you get a thin strip of the chromosphere showing which works the same as a slit in a spectrograph and you can get the spectra of the suns atmosphere. From left to right is red H-alpha, yellow Helium, light Blue H-beta and violet H-gamma. Even though it's out of focus, I was pleased to get the Helium as that's how it was initially discovered (hence Helium from Helios, the greek Sun God).

IMAGE LINK: http://www.flickr.com/​photos/stevetla/830856​7319/

Very very cool - precisely what I intend of doing....

What's your strategy in identifying the gases you mention? One of the calibration software that was mentioned, or you compare with individual spectres of known substances?

With the Sun, it's reasonably straight forward to identify the lines as it's predominantly Hydrogen and Helium. The hard part is that you can only do what I've done at a total solar eclipse as it uses the moon to block out the bright bit and just leave a thin sliver of solar atmosphere. That's an emission spectra, like your lamp.
If you do a solar spectra at any other time, you'll have a continuous rainbow with some dark absorption lines in it and they correspond to the different elements in the same way.

To identify which is which, you pretty much do what you've done with a lamp with a known gas in it. Many spectrophotometers have a neon lamp built into them for that reason.
As long as you use the same lens and grating in the way that you've done it, you just need one calibrating image that shows both the spectrum and the light source (called the zero order image). If you can identify two lines and measure the distance (in pixels) from the zero order image to the lines, you can work out the wavelength of any of the other lines and then look them up.
The software does all that for you.

A simple way to get a solar spectrum is to use a needle on a bit of black card. The needle reflects a thin line of sunlight and when you photograph that through your diffraction grating, you see the spectrum with the black background. If your needle is smooth, you should be able to resolve some of the wider absorption bands.

Steve.