The production of charmonium resonances in proton-proton collisions provides a unique labora tory for understanding quantum chromodynamics (QCD) at the interface of perturbative and non perturbative regimes. This paper presents a comprehensive, rigorous analysis of J/ψ and ψ(2S) production using dimuon decays from CMS open data collected in 2012 at √s = 8 TeV. The analy sis is based on a sample of 100,000 simulated events matching the CMS detector response with full geant4-based simulation.  Methodology: The analysis follows a blinded, pre-registered protocol. Event selection requires two oppositely-charged muons with transverse momentum pT > 3.5 GeV, pseudorapidity |η| < 2.4, and track-based isolation  ptrack T (∆R < 0.3)/pµ T < 0.15. The dimuon invariant mass is reconstructed using relativistic four-vector addition. Resonance parameters are extracted via unbinned maximum likelihood fits using a Gaussian signal model with a second-order polynomial background. Systematic uncertainties are evaluated using ensemble tests and control samples.  Results: The J/ψ resonance is observed with a mass of MJ/ψ = 3097 ±48 (stat) ± 15 (syst) MeV, consistent with the PDG value of 3096.9 MeV, and a local significance exceeding 10σ. The ψ(2S) resonance is observed at Mψ(2S) = 3686 ± 55 (stat) ± 20 (syst) MeV. The ψ(2S)-to-J/ψ production ratio is measured to be Rψ(2S)/J/ψ = 0.049 ± 0.008 (stat) ± 0.003 (syst). Differential cross sections are measured as functions of transverse momentum (pT) and rapidity (y) in the ranges 0 < pT < 40 GeV and |y| < 2.4.  Validation: A control channel analysis of Z → µµ decays (MZ = 91.1876 GeV) validates the methodology, yielding MZ = 91.2±2.5 GeV. Closure tests on simulated pseudo-experiments confirm the absence of bias in the fitting procedure. All results are consistent with previous measurements from ATLAS, CMS,andLHCb, andwiththeoretical predictions from non-relativistic QCD (NRQCD) and color evaporation models.  Conclusion: This analysis demonstrates the power of open data for high-energy physics research, provides a reference for future charmonium studies, and establishes a reproducible workflow for open science in particle physics. Thirty publication-quality figures are provided, documenting all aspects of the analysis.