Abstract We present the first public data release of the DDO51 band from the Stellar Abundances and Galactic Evolution Survey (SAGES), based on Nanshan One-meter Wide-field Telescope observations obtained between 2023 September and 2024 January. This release initiates the DDO51-band component of the survey, covering ∼2500 deg 2 of the northern sky and including more than 10 million sources. The DDO51 filter is centered near the Mg i b triplet and the adjacent MgH feature, offering sensitivity to stellar surface gravity. The data reduction pipeline incorporates an improved astrometric solution anchored to Gaia DR3 and a photometric calibration strategy tied to synthetic photometry from Gaia XP spectra. These procedures yield a point-source depth of ∼18.9 mag at a signal-to-noise ratio ∼10 and an internal photometric precision ≈6–7 mmag at the bright end. A preliminary color–color analysis using Gaia broadband photometry confirms the expected sensitivity of the DDO51 band to stellar surface gravity, demonstrating a clear photometric separation between dwarf and giant sequences for late-type stars. This dataset, when combined with existing SAGES photometry in other bands, provides a crucial tool for disentangling the substructures of the Milky Way. All data products from this release are available upon publication.
Zhang et al. (Fri,) studied this question.