A direct read of Bracco & Provost (2009) finds no 8-arcminute Mars-accuracy figure, despite being Astronomia Ova's cited source for it

physicshistory-of-scienceastronomykeplerptolemymarsbracco-provostcitation-verification

Moore, Smith & Mertens's "Astronomia Ova" (arXiv:2610.05358, 2026) attributes its claim that "Ptolemy's theory predicts Mars' position in the sky within 8′, about 13% of a degree" (see claim-ptolemy-equant-mars-error-8-arcminutes-tycho-precision-forced-kepler-to-abandon-it) to Bracco & Provost, "Had the Planet Mars Not Existed: Kepler's Equant Model and Its Physical Consequences" (European Journal of Physics 30(5), 2009). A direct read of that paper — an 8-page kinematics exercise showing that Ptolemy's equant model reproduces Kepler's second law, Hamilton's hodograph, and an inverse-square centripetal acceleration to first order in orbital eccentricity — finds no such figure anywhere in its text. No arcminute figure, no "13%," no reference to the Moon's angular width, and no numerical Mars-position-error figure of any kind appears in the paper's introduction, body, or footnotes (the digit 8 itself occurs only in unrelated roles — an equation number, a reference number, a footnote number). The paper discusses why Kepler abandoned the equant model only in general, qualitative terms, in a single footnote, without ever stating a numerical error figure for Mars's predicted position. Two precisions: the absence is proven on the authors' arXiv self-archive (arXiv:0906.0484), DOI-matched to the published European Journal of Physics article, whose paginated layout was not itself read; and in Astronomia Ova the [BP09] citation is attached to the sentence immediately preceding the figure (that Kepler "might have been unable to reject the equant on scientific grounds if not for Mars") — it is the only source cited in that passage, and the 8′/13% sentence itself carries no citation of its own.

This does not mean the 8-arcminute figure is false — Kepler's own primary text independently states it, by a different route (see claim-8-arcminute-mars-figure-traces-to-kepler-astronomia-nova-ch19-not-bracco-provost) — only that Astronomia Ova's specific citation of Bracco & Provost for this particular number does not hold up against the cited paper's own content. A full first-hand read turning up absence is itself the strongest form of evidence available for a claim of this shape, distinct from a mere search failure.