
Following the study of HeII4686, here is the HeI 5876 extracted from an order of an eshell spectrum of 9600s exposure and sampled to 3600s and 7200s for comparison.
SNR is better than in the blue region, normal with the better sensitivity of the ccd, SNR50 around 5972A.
Straight absorption are Na-D interstellar absorption, with a bump inside. "The bumps in the core of the NaI D-lines is due to two present components. One forms in our spiral arm, the other one forms in the next spiral arm. Typically this is a sign of a...
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