A Statistical Agreement Analysis Between a DIY Photometric Device and a Calibrated Sky Quality Meter Using Bland-Altman and Passing-Bablok Methods
Judhistira Aria Utama1,2 - Cahyo Puji Asmoro1,2

1 Physics Study Program, Faculty of Mathematics and Natural Sciences, Universitas Pendidikan Indonesia, Bandung, Indonesia

2 Center of Excellence on Astronomical Data Science and Light Pollution, Universitas Pendidikan Indonesia, Bandung, Indonesia

Abstract

This study presents a statistical evaluation of the Fotometer DIY CJ01, a compact photometric device developed as an accessible alternative to the Unihedron Sky Quality Meter (SQM) for assessing light pollution levels. Comparative night-sky brightness data were collected from both instruments under synchronized one-minute observation intervals. Agreement and bias between the two measurement systems were quantitatively assessed using the Bland-Altman method and further examined through Passing-Bablok (Theil-Sen) regression analysis. The results indicate a systematic bias that exceeding the nominal systematic uncertainty of the SQM. The derived regression model suggests that applying a constant offset correction can enhance the DIY instrument^s consistency with the calibrated reference. These findings emphasize the utility of robust nonparametric regression and agreement analysis for evaluating measurement reliability in low-cost photometric systems, thereby bridging the methodological gap between citizen-science instrumentation and formal quantitative modeling.

Keywords: Agreement analysis- Bland-Altman method- Passing-Bablok regression- Theil-Sen estimator- Measurement bias- Calibration model- Photometric data- Light pollution assessment.

Topic: Mathematics and Mathematics Education