I created this forum about a year ago as a place to collect spectroscopic images. I thought maybe a very brief and amateurish introduction to spectroscopy might help set some context. Caveat: I am a raw amateur with regards to spectroscopy. There are many others who are more experienced and/or who have produced better and more interesting results than I have with even more basic equipment. So this is a little bit of what I know, but if you want to learn more there are many better sources.
Spectroscopy is the analysis of stars and other bodies by examining the wavelengths of light they emit or absorb. If you've performed any sort of narrowband imagining, you're familiar with emission nebula that emit Hydrogen Alpha, Oxygen-iii or Sulfur-ii emissions: very specific wavelengths of light created by very specific energy transitions within the elements' atoms. Those transitions are the basis of spectroscopy, and account for the lion's share of astronomical discoveries. The composition of stars and nebula, red shift and blue shift, star temperatures and luminosity, galaxy and star rotational speeds, etc., are all related to the spectra of light emitted by those bodies.
Getting started is easy. You need some way to create a spectral image. A diffraction grating which fits your filter wheel or camera nose will do the job. Many folks start with a Paton Hawksley Star Analyser (e.g. https://www.rspec-astro.com/star-analyser/ ) . Put it in your filter wheel or in your camera nose, align it with the long edge of your sensor, and off you go. You can certainly obtain more refined and advanced equipment, but basic diffraction grating will get you started.
I start by focusing with a luminance filter, and then refocusing inward a fixed amount that I've determined by trial and error. You want the lines in the spectrum to be sharp: it's okay and and even expected that the star is a little out of focus.
Once you've captured a reasonable spectrum -- sharp lines, no clipping on the high (white) end of the signal -- you use specialized software to calibrate and analyze it, such as RSpec ( https://realtime-spectra.com/collections/astronomical-spectroscopy/products/copy-of-rspec-astronomical-spectroscopy-software ). There are others: I've used RSpec but you might prefer something else. Whichever way, with software assistance you can calibrate your spectrum, adjust it for your camera response, and begin the analysis.
Like I said, I'm a raw amateur, so I've been satisfied with getting calibrated curves that somewhat resemble professionally developed curves for the same classes of stars. I've also played around with trying to predict star surface temperatures based on my spectra, and that's a whole area of learning in itself. But mostly, I've found it very satisfying to take a spectrum and see with my own eyes, with data coming from my own equipment, that yes: some stars have strong Balmer (hydrogen lines), some stars absorb strongly on titanium and other less common elements, Wolf-Rayet stars are wildly different, and there really is a change in spectrum as you move from hot O-class stars to the cool M-class. Maybe I'm not discovering anything new, but I'm seeing the basics of the science for myself, and it is real. That is exciting.
So that's the story. I'm hoping that if there are other spectrographers lurking out there, they might add their images here, and if you decide to give it a go, I hope you'll share your results. I still like to take pretty pictures, but there is still a lot of reward in the more basic practice of collecting spectrums: your rig starts to become an instrument for collecting quantitative data, not just qualitative, and to me that's pretty cool.
Spectroscopy is the analysis of stars and other bodies by examining the wavelengths of light they emit or absorb. If you've performed any sort of narrowband imagining, you're familiar with emission nebula that emit Hydrogen Alpha, Oxygen-iii or Sulfur-ii emissions: very specific wavelengths of light created by very specific energy transitions within the elements' atoms. Those transitions are the basis of spectroscopy, and account for the lion's share of astronomical discoveries. The composition of stars and nebula, red shift and blue shift, star temperatures and luminosity, galaxy and star rotational speeds, etc., are all related to the spectra of light emitted by those bodies.
Getting started is easy. You need some way to create a spectral image. A diffraction grating which fits your filter wheel or camera nose will do the job. Many folks start with a Paton Hawksley Star Analyser (e.g. https://www.rspec-astro.com/star-analyser/ ) . Put it in your filter wheel or in your camera nose, align it with the long edge of your sensor, and off you go. You can certainly obtain more refined and advanced equipment, but basic diffraction grating will get you started.
I start by focusing with a luminance filter, and then refocusing inward a fixed amount that I've determined by trial and error. You want the lines in the spectrum to be sharp: it's okay and and even expected that the star is a little out of focus.
Once you've captured a reasonable spectrum -- sharp lines, no clipping on the high (white) end of the signal -- you use specialized software to calibrate and analyze it, such as RSpec ( https://realtime-spectra.com/collections/astronomical-spectroscopy/products/copy-of-rspec-astronomical-spectroscopy-software ). There are others: I've used RSpec but you might prefer something else. Whichever way, with software assistance you can calibrate your spectrum, adjust it for your camera response, and begin the analysis.
Like I said, I'm a raw amateur, so I've been satisfied with getting calibrated curves that somewhat resemble professionally developed curves for the same classes of stars. I've also played around with trying to predict star surface temperatures based on my spectra, and that's a whole area of learning in itself. But mostly, I've found it very satisfying to take a spectrum and see with my own eyes, with data coming from my own equipment, that yes: some stars have strong Balmer (hydrogen lines), some stars absorb strongly on titanium and other less common elements, Wolf-Rayet stars are wildly different, and there really is a change in spectrum as you move from hot O-class stars to the cool M-class. Maybe I'm not discovering anything new, but I'm seeing the basics of the science for myself, and it is real. That is exciting.
So that's the story. I'm hoping that if there are other spectrographers lurking out there, they might add their images here, and if you decide to give it a go, I hope you'll share your results. I still like to take pretty pictures, but there is still a lot of reward in the more basic practice of collecting spectrums: your rig starts to become an instrument for collecting quantitative data, not just qualitative, and to me that's pretty cool.
