Precision distance to Galactic Cepheid variables with infrared observation

我们在购买的底座上安装了一个现有的40cm望远镜管，实现了全自动观测，没有其他系统可以对造父变星星团进行红外观测，我们在望远镜上安装了一个现有的红外相机。我们改进了相机的冷却能力，以便进行更长时间的自动观察。在观察了几个集群之后，我们发现该相机的信噪比比预期差了五倍。这个噪声问题使我们只能在1 Kpc范围内观察聚类。因此，我们将分析重点放在M25和NGC1647上，发现来自尘埃吸收的误差贡献与之前在可见光波段的观测结果相比减少了四分之一。在观测的同时，我们强调了等时线的改进和金属丰度的重要性。我们发现现有的B-V变换存在很大的不确定性。利用现代更新的数据库和金属依赖性，我们得到了更好的修正B-V变换（AJ in press）。在金属丰度方面，我们推导出了一个用uv光度法估算金属丰度的新公式。

We have installed an existing 40cm telescope tube onto the purchased mount resulting in fully automatic observation, No other system exists for infrared observing of stellar-clusters with Cepheid variables, We installed an existing IR-camera to the telescope. We improved the camera's cooling capacity for longer automatic observation. After observing several clusters, we found that singal-to-noise ratio of that camera is five times worse than expected. This noise problem allows us to observe clusters only within 1 Kpc. We therefore focused our analysis on M25 and NGC1647 and found that the error contribution from dust absorption was reduced by a factor of four compared to previous observation in visible wavelength. Parallel to the observation, we put emphasis on the improvement of isochrone and on importance of metallicity. We found the existing B-V transformation contains large uncertainty. Using the modern updated database and metallicity-dependence, we derived better revised B-V transformation (AJ in press). As far the metallicity, we derived a new formula to estimate metallicity from UBV photometory (in preparation).