7.2 The Observations

Infrared photometry of the sample was obtained on the nights of 1999 September 28-30 the using 155cm Carlos Sanchez Telescope (TCS) equipped with the CV F photometer. The filters used were the JHK filters of the TCS system (Alonso et al., 1998). Standard stars taken from the UKIRT bright standards list (the UKIRT system is that defined by the UKIRT standards list, observed by the UKT9 photometer) were observed at high and low air masses roughly once per 90 minutes. The standard methods of photometric data reduction were applied, with airmass corrections derived on a per filter, per night basis. Colour corrections from Alonso et al. (1998) and Leggett (1992) were used to convert the UKIRT standard magnitudes to the TCS system for reduction. After reduction in the TCS system, the final magnitudes were then converted to the standard CIT system (Elias et al., 1982), and it is these magnitudes that we present in Table 7.1. For those stars observed more than once we give a mean value, with the number of observations identified in brackets after each entry. The original sample contains 58 Be stars from O9B8.5, however because of observational constraints the sample has been reduced, in this chapter, to 52 objects.