PG 1302−102 has unequal mean ZTF DR24 magnitudes in eight interval pairs 1,884 days apart

We test whether public ZTF Data Release 24 magnitudes of the quasar PG 1302−102 repeat after fixed published periods. We use 218 g and 232 r measurements and compare mean magnitudes in 30-day intervals. The primary shift is 1,884 days. Each interval must contain at least three accepted measurements. Six g pairs and two r pairs pass. We subtract a shared magnitude shift measured from nearby sources on each target exposure. The corrected later minus earlier differences range from −0.112 to +0.235 mag in g and from −0.072 to +0.115 mag in r. The RMS differences are 0.1696 and 0.0959 mag. After removal of a constant mean difference, they are 0.1148 and 0.0935 mag. Nearby sources have smaller differences on the same intervals. The accepted widths cover only 9.6% of a cycle in g and 3.2% in r. Shifts of 2,012.6 and 2,296 days each give only two g pairs and no r pairs, so these data do not support a fair period ranking. All selected target data use CCD 6, for which the release notes warn of a calibration bias. The local correction does not establish removal of source-dependent errors. The result is a verified set of interval differences, not a physical period measurement or a test that excludes a black hole pair. We provide raw responses, exact queries, hashes, all tested settings, source code, figures and independent arithmetic checks.

PG 1302-102 · quasar variability · ZTF DR24 · optical recurrence · black hole binary candidate · public astronomical data · ensemble photometry · reproducible research