Photometric calibration of the Stellar Abundance and Galactic Evolution Survey (SAGES): Nanshan One-meter Wide-field Telescope g, r, and i band imaging data
Uniform and accurate flow calibration is the difficulty and core of large-field photometric survey data processing. This article uses LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope) DR7 spectral data, corrected Gaia EDR3 photometric data and Gaia photometric abundance data, using The Nanshan 1-meter large-field telescope was constructed using the spectrum-based SCR (Stellar Color Regression) method and the photometry-based SCR method (SCR′ method). There are more than 2.6 million standard stars with an accuracy of about 10 to 20 millimagnitude in the g, r, and i bands, and then SAGES (Stellar Abundance and Galactic Evolution) The photometric data of a sky area of about 4254 square degrees taken by the Nanshan 1-meter telescope were relative flow calibrated. In this process, we carefully considered the calibration The zero mark changes with different images (time), different channels of the detector and star images at different positions of the detector. Based on the modified Pan-STARRS (PS1) Based on the DR1 photometry data, absolute flow calibration was performed, and the mutual conversion relationship between the calibrated magnitudes of the Nanshan g, r, and i bands and the PS1 magnitude was given. The internal consistency test of the calibration accuracy was performed based on the common source between adjacent images, and it was found that the calibration accuracy of the three bands was approximately 2.0 millimagnitude. At the same time, we The calibration accuracy was also tested externally, using the PS1 magnitude synthesized by Gaia DR3 seamless spectrum. It was found that the calibration uniformity at 1.3° resolution was 2.4, 2.3 and 0.9 millimagnitude. In addition, this article also discusses the changes in relative gain with time between the stellar flat field and the detector channel.