Origin of discrepancies in measured filter transmission profiles

Identify the origin of the discrepancies between the measured and catalog transmission characteristics of the DOLPHIN Na D and Hα filters, including the broader-than-specified Na D passband and lower-than-specified Hα peak transmission.

Background

The in-system transmission measurements found that the Na D filter has a full width at half maximum of approximately 2.232 nm, about twice its catalog specification, while the Hα filter has a measured peak transmission of approximately 75%, lower than the catalog value. The measured central wavelengths were consistent with the manufacturer specifications within the measurement resolution.

The paper leaves the cause of these discrepancies unresolved. It identifies several possible contributors, including DOLPHIN’s optical configuration, filter manufacturing tolerances, and systematic uncertainties in the fiber-coupled transmission-measurement setup. Resolving the cause would improve confidence in the filter characterization and inform future forward models of expected absorption signals.