An Exposure Time Calculator for the 2.4m Telescope of the Yunnan Observatory

Currently,many foreign observatories provide the exposure time calculators (ETCs)for their observational systems, while few people carry out such work in China.An ETC is important for the observers who are unfamiliar with the observational system to plan for observations.The ETC of the 2.4m telescope at the Gaomeigu Station of the Yunnan observatory can give a referential value about the needed exposure based on the parameters of telescope and instruments.Observers can know the feasibility of the desired observations,determine the optimal exposures,or estimate the signal-to-noise ratios (SNRs)of objects according to the given values.From the comparison with the photometric data of standard stars,we have found the results of our ETC to be reliable.