Abstract
A set of infrared standard stars for the South African Astronomical Observatory (SAAO) (Carter 1990) are observed from the Observatorio Astron6mico Nacional (QAN) located at Sa, Pedro Martir (SPM) in northern Mexico. A number of linear transibrmation equations is obtained; in them, there is a slight need for a colour term which implies that both sets of filters have slightly different values for their effective wavelengths. Values for the OAN mean extinction coefficients are calculated. They are larger than the values reported in Carrasco et al. (1991); this might, however, be due to the ash and debris deposited on the atmosphere by recent volcanic eruptions. We also calculate a set of colour transformations to the homogeneous IR photometric system proposed by Bessell & Brett (1988).
