The open clusters NGC 2323 and NGC 2539 have been analysed using CCD $$U\!B\!V\!(R\!I)_{KC}$$ photometric data, observed at the San Pedro Martir Observatory. Cluster memberships have been determined with the proper motion and parallax measures from the GaiaDR2 astrometric data release. Photometric metal and heavy element abundances have been obtained as $$([M/H],\;Z) = (-0.10,~0.012)$$ (NGC 2323) and $$(-0.31,\;0.007)$$ (NGC 2539) from the $$\delta (U$$ –B) technique in the two-colour diagrams, which are used to select the appropriate PARSEC isochrones. The estimated reddening of NGC 2323 is $$E(B-V)=0.23\pm 0.04$$ using 11 early type stars. For NGC 2539, we find $$E(B-V)= 0.02\pm 0.06$$ . For $$(B-V)$$ colour, distance moduli and distances for NGC 2323 and NGC 2539 are derived as $$(V_{0}-M_V, d\ \mathrm{(pc)}) = (10.00\pm 0.10, 1000\pm 50)$$ and $$(V_{0}-M_V, d \mathrm{(pc)}) = (10.00\pm 0.04, 1000\pm 20)$$ , respectively. The median GaiaDR2 distance $$d=1000\pm 140$$ pc ( $$\varpi =0.998\pm 0.136$$ mas) for the likely members of NGC 2323 is in concordance with its four-colour photometric distances 910–1000 pc. For NGC 2539, its GaiaDR2 distance $$d=1330\pm 250$$ pc ( $$\varpi =0.751\pm 0.139$$ mas) is close to its four-colour photometric distances, 1000 pc. Fitting the PARSEC isochrones to the colour magnitude diagrams (CMDs) gives an old age, $$890\pm 110$$ Myr, for NGC 2539. Whereas NGC 2323 has an intermediate age, $$200\pm 50$$ Myr. One red clump/red giant candidate (BD-12 2380) in the CMDs of NGC 2539 has been confirmed as a member in terms of the distances $$d_{I} =950\pm 50$$ pc and $$d_{V}=910\pm 90$$ pc of VI filters within the uncertainties, as compared to the distance $$1000\pm 20$$ pc of NGC 2539. This giant’s GaiaDR2 distance ( $$d=1200\pm 70$$ pc) is not close to these photometric distances.

中文翻译：

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CCD $${U\!B\!V\!(R\!I)}_{KC}$$ UBV ( RI ) NGC 2323 和 NGC 2539 疏散星团的 KC 光度测量

疏散星团 NGC 2323 和 NGC 2539 已使用 CCD $$U\!B\!V\!(R\!I)_{KC}$$ 光度学数据进行分析，这些数据是在圣佩德罗·马蒂尔天文台观测到的。星团成员是通过 GaiaDR2 天体测量数据发布的自行和视差测量确定的。光度金属和重元素丰度已获得为 $$([M/H],\;Z) = (-0.10,~0.012)$$ (NGC 2323) 和 $$(-0.31,\;0.007)$$ (NGC 2539) 来自双色图中的 $$\delta (U$$ –B) 技术，用于选择合适的 PARSEC 等时线。NGC 2323 的估计红化为 $$E(BV)=0.23\pm 0.04$$ 使用 11 颗早期类型恒星。对于 NGC 2539，我们发现 $$E(BV)= 0.02\pm 0.06$$ 。对于 $$(BV)$$ 颜色，NGC 2323 和 NGC 2539 的距离模数和距离推导出为 $$(V_{0}-M_V, d\ \mathrm{(pc)}) = (10.00\pm 0.10, 1000\pm 50)$$ 和 $$(V_{0}-M_V, d \mathrm{(pc)}) = (10.00\pm 0.04, 1000\pm 20)$$ 。可能是 NGC 2323 成员的 GaiaDR2 距离中值 $$d=1000\pm 140$$ pc ( $$\varpi =0.998\pm 0.136$$ mas) 与其四色光度距离 910-1000 pc 一致. 对于 NGC 2539，它的 GaiaDR2 距离 $$d=1330\pm 250$$ pc ($$\varpi =0.751\pm 0.139$$ mas) 接近它的四色光度距离，1000 pc。将 PARSEC 等时线拟合到色等图 (CMD) 中，NGC 2539 的年龄为 $890\pm 110$$Myr。而 NGC 2323 具有中间年龄，$200\pm 50$$Myr。根据距离$$d_{I} =950\pm 50$$ pc 和 $$d_{V }=910\pm 90$$ pc 的不确定度内的 VI 过滤器，