Systematic characterization in hydrogen 2S-8D spectroscopy.

We will present progress in measuring the 2S-8D transition in hydrogen using a cryogenic metastable hydrogen beam (approx. 5 K), with a focus on the characterization of key systematics surrounding this measurement.~ In particular, we will present a characterization of the residual Zeeman shifts and measurements of the 2S-12D lineshape, which is used to characterize DC Stark shifts within the apparatus.~ The measurement of the 2S-8D transition in hydrogen can be used to determine the proton charge radius and the Rydberg constant.