Fundamental astrophysical parameters have been derived for Berkeley 55 (Be 55) open cluster based on the UBVI charge-coupled device (CCD) photometric data observed using a AZT-22 1.5 m telescope at Maidanak Astronomical Observatory (MAO) in Uzbekistan. The mean reddening is obtained as \(E(B-V)=1.77\pm 0.10\,\mathrm {mag}\) from early-type members. The zero-age main sequence fitting in the \(Q_{V\lambda }\) – \(Q'\) diagrams indicates the distance modulus, \((V_{0}-M_{V})=12.4\pm 0.20\,\mathrm {mag}\,(d=3.02\pm 0.28\,\mathrm {kpc}\)). This photometric distance is consistent with the distances of Gaia EDR3 (\(d = 3.09 \pm 0.16\,\mathrm {kpc}\)) and period–luminosity relation (\(d =\) 2.78 ± 0.32 kpc) of its Cepheid S5 within the uncertainties. This distance also locates the cluster near the Perseus spiral arm. The Geneva isochrone fittings to the Hertzsprung–Russell diagram and observational colour–magnitude diagrams derive turn-off age, 85 ± 13 Myr, by taking care of five red supergiants/bright giants. The possible inconsistencies in the locations of the bright giants with the rotating/non-rotating isochrones may be due to both the age spread of stars in young open clusters and the diversity in rotational velocities.

基于使用 AZT-22 1.5 m 望远镜在乌兹别克斯坦 Maidanak 天文台 (MAO) 观测到的 UBVI 电荷耦合器件 (CCD) 光度数据，已经推导出了伯克利 55 (Be 55) 疏散星团的基本天体物理参数。平均红化是从早期类型成员获得的\(E(BV)=1.77\pm 0.10\,\mathrm {mag}\)。\(Q_{V\lambda }\) - \(Q'\)图中的零龄主序拟合表示距离模量，\((V_{0}-M_{V})=12.4\pm 0.20 \,\mathrm {mag}\,(d=3.02\pm 0.28\,\mathrm {kpc}\) )。这个光度距离与 Gaia EDR3 的距离（\(d = 3.09 \pm 0.16\,\mathrm {kpc}\)）和周期-光度关系（\(d =\)2.78 ± 0.32 kpc) 其造父变星S 5 内的不确定性。这个距离也位于英仙座旋臂附近的星团。Hertzsprung-Russell 图和观测色-星等图的日内瓦等时线拟合通过照顾五颗红超巨星/亮巨星推导出关闭年龄 85 ± 13 Myr。明亮巨星的位置可能与旋转/非旋转等时线不一致，这可能是由于年轻疏散星团中恒星的年龄分布和旋转速度的多样性。