Timing analyses of accreting black holes often package nodal information in ways that depend on benign choices of time and azimuthal convention. We identify the corresponding pipeline-invariant content for slightly tilted circular rings and express it as an orbital nodal phase, Δψ orb . In Kerr, this quantity gives the clean geodesic baseline for nodal timing: it equals the nodal precession per orbit, is invariant under the benign remappings considered here, and decreases monotonically with radius outside the innermost stable circular orbit. A fixed-Ω φ . response framework then isolates genuine metric sensitivity from trivial radius drift and yields a leading far-field quadrupolar response that falls as r −3 . Two small analysis-level corrections are also identified, namely a second-order bias from coherent radial breathing and a geometric offset from slow two-parameter loops. A limited published-data illustration for GRO J1655.40 shows that the observational proxy for Δψ orb can be reconstructed directly from standard reported quasi-periodic oscillation frequencies once an orbital-frequency anchor and an identification convention are specified. Within the thin-ring limit, Δψ orb therefore provides a pipeline-robust reporting quantity and a Kerr-baseline diagnostic for source-level, simulation-level, and strong-gravity applications.
Mehmet Baran Ökten (Sat,) studied this question.