1947 Iso-Heikkilä: 2026 Las Cumbres Observatory lightcurve photometry and analysis code

Reduced photometry, analysis code, and figures for 1947 Iso-Heikkilä, observed on 2026 August 19-20 with the Las Cumbres Observatory 0.4-m telescopes (Sloan r′, 150-s exposures; SAAO and Haleakala nodes; proposal LCOEPO2018A-009, LCO requests 4334532 and 4358995). The asteroid crossed a crowded field in Sagittarius. Magnitudes are calibrated to ATLAS-RefCat2 r using an ensemble of 40 comparison stars through LCO BANZAI zero points. Light from blended field stars was measured in exposures taken when the asteroid was elsewhere and subtracted. The method was checked with blank-sky tracks and an injected constant source. Result: amplitude 0.06 ± 0.02 mag and a tentative synodic period of 3.65 ± 0.15 h, consistent with Stone (2026, Minor Planet Bull. 53, 49-51). A 0.35-mag lightcurve at 5.0158 h (Galád 2010) is excluded. Contents: the full 168-point lightcurve (CSV), the 106 unblended points in ALCDEF format, the comparison-star list, numerical results, figures, and the complete Python pipeline (run_all.sh). Data and figures are CC BY 4.0; code is MIT. Supplementary data for: Nayak, A., "Lightcurve of 1947 Iso-Heikkilä Observed Across a Crowded Milky Way Field," submitted to the Minor Planet Bulletin.