Left: MCELS Hα image of SGS LMC 1. The 25′ radius circular region is plotted in a red dashed line. The OB association LH15 is radially divided into A, B, and C regions. The stellar population is examined inside and outside LH15, and in the A, B, and C regions of LH15 separately to search for variations. Right: MCELS Hα image of SGS LMC 1 marked with main-sequence stars in the mass ranges of 10–15, 15–20, and 20–25 M_⊙.