Abstract

NUNEZ, J. M. et al. Intercalibration of the San Pedro Mártir and ctio dimm units. Rev. mex. astron. astrofis [online]. 2007, vol.43, n.2, pp.283-290. ISSN 0185-1101.

We compare simultaneous seeing measurements produced by the differential image motion monitor (DIMM) units used at the Observatorio Astronómico Nacional at San Pedro Mártir (SPD) and at Cerro Tololo Inter-American Observatory (RoD), for a total of 14 nights. For the data set, made of 1581 nearly-synchronous measurements, we find that the mean and median RoD-SPD seeing differences are +0.004±0.138" and +0.010" respectively. We also find that the median of the RoD-SPD seeing measurements is +0.041" when seeing is less than 1", -0.032" when it is between 1" and 1.5", and -0.292" when it is larger than 1.5". Since seeing is usually smaller than 1", we conclude that measurements obtained with SPD-like units should be increased by 0.01" to 0.04" when comparisons are made with sites using RoD-like units. This correction is much smaller than the natural dispersion of seeing measurements along any night, and it makes sense only when operational conditions in both sites are practically the same.

Keywords : Site testing.