As a contrast to the distant quasars , here are some spectra of similarly old but still nearby population II halo starswith very low metal content. (Cosmological expansion was evidently no match for local gravity !)
Thanks! Like most amateurs, I do a lot observing and not enough reading and studying. I do tell my friends that the stars are pretty at any magnification but if you do not understand what you are looking at, you are missing the essence of the experience.
I am impressed with your instrumentation, the very fact that you have it. The American Astrnomical Society has (another new) initiative to reach out to its amateur affiliates and – with the purchase of Sky & Telescope – to amateurs in general. The story line is that in the 1920s when professionals were using sophisticated and expensive equipment, amateurs drifted away from the AAS. That may be true. But the fact is that now, just for example, you have basically consumer goods that would have been science fiction 100 years ago.
I just attended two AAS conferences this year, the 237th General Assembly and the 54th Dynamical Division. There were some interesting papers, but most of what I saw lacked what (if I may) I typify as British empiricism, you know, actually kicking the rock. So, I downloaded your graphs to a folder on my computer for Spectroscopy.
All of that is to say “thanks” for expanding my understanding.