Photometry of CGCS 6306. A: Light curves from ASAS-SN, ATLAS, and Gaia. The dotted gray sinusoidal line represents the apparent long-term variability trend. The vertical lines in the light curves mark the observation time of the LAMOST (2015 March 11) and NOT/FIES (2025 February 25) spectra. B: Lomb-Scargle periodograms of the photometric data. Due to the short time span of ASAS-SN and GaiaG observations, their periodograms are shown as dotted lines only. C: Phase-folded light curves of CGCS 6306. The long-term sinusoidal trend has been removed, and the median magnitude was subtracted for clarity.