Sad and embarrassed that no one else in this forum seemed to be having as much trouble as me. At first I was thinking, "I understand that this is a shift cypher, but shifting V 497 letters to the left seems odd and extreme lol.", and even once I understood that I was supposed to be subtracting the numbers up top from the numbers on the reference spectrum, I still couldn't figure out if red or blue was negatives or positives, or how I was supposed to know which stupid little lines were originally which on the tiny little barcode, so I've decided to just give up. Physicists have it hard, man.

It is due to the position on the light spectrum, galaxy F corresponds to the first of the 3 bars referenced on the unshifted spectrum from 550-650nm so it is shifted to that value

Process of ‘shifting’ and Id-ing the ‘new’ galaxy led me to ignore my conclusion for Galaxy F. I don’t understand how (-18) is answer and not (-2)?? Why is it different? But I had 9 correct letters, so I substituted. I can live with this anomaly🤨

Great puzzle! I noticed that the lay-out of each galaxy label was unique in its horizontal positioning and I wish that the answer required us to sort the shifted letters by the each galaxy's relative position (i.e. a nod to the light spectrum) rather than just reading the letters top-to-bottom but it was fun to learn about light and the Doppler effect!

Wow! As an astrophysicist, this was an awesome puzzle.

It is 18 off of where it should be, which is 571 on the Unshifted Reference Spectrum. Treating the alphabet like a circle and going back 18 lands on N.

Shouldn’t galaxy F be shifted to “D” instead of “N”? Shifting to N skips over 587 nm