Hi all,
I need feedback from experienced amateur spectroscopists (all of you I think 
), about my ability to correctly recognize element lines into an HR spectrum near Halpha. This is important to understand if I’m going into the right direction or not.
I reworked a VV Cep spectrum taken in oct 2025 and recalibrated in wavelenght on the metallic lines of the M component; this is to cut any shift due to calibration lamp.
Current line database which comes with programs (AllElements.dat in BASS) do recognize a few lines, so I downloaded more lines from NIST Atomic Spectra Database | NIST.
Result is:
Now the question is:
which line is correctly identified, and which is not?
I know this is time consuming for anybody, but I want to thank you just if you read this post.
As a complement any direction about my need of information is welcome:
it is likely all the major lines I could not identify are blends or lines/bands from diatomic molecules; are you aware of any source database for simple molecular lines (TiO, VO, CH…)? I expect these are in the spectrum, infact it is an M star!
Greetings
RP
Many of the IDed lines are Fe and Ca, which is not surprising. It looks like most are correctly identified to me.
Molecules will not have small, well-defined lines like these - they are larger (and usually asymmetric) depressions in the spectrum.
-Kenneth
You cannot use the lines in the star for calibration as the wavelength will depend on the radial velocity of the star and our velocity round the sun (and potentially pulsations of the star). If you want to check your calibration you can use the Telluric (water) absorption lines from our atmosphere which are numerous around H alpha. If you are using ISIS software for example this has a tool to identify these and you can then adjust the spectrum calibration to match the wavelengths.
Cheers
Robin
The problem is identifying them in cool stars which have so many other lines. This is why it is important to have a stable spectrograph and a calibration lamp setup that mimics the optical path of the star as closely as possible so you can trust the calibration produced by the calibration lamp. (Unstable soectrographs give nothing but grief)
Thank you for your replies:)
This execise is intended to familiarize with cool stars spectra I found very hard to calibrate with H2O telluric lines. VV Cep is easy because H2O are still prominent.
I find identifiyng lines at rest wavelength an easier task only to familiarize with them; as you said this has no scientific value.
Cheers
Rosario
), about my ability to correctly recognize element lines into an HR spectrum near Halpha. This is important to understand if I’m going into the right direction or not.