sentences:  Due to the extremely high interstellar reddening towards Wd1, it is very difficult to observe in the U- and B-bands, and most observations are made in the R- or I-bands at the red end of the spectrum or in the infra red.Stars in the cluster are generally named using a classification introduced by Westerlund, although a separate naming convention is often used for the Wolf-Rayet stars.At X-ray wavelengths, Wd1 shows diffuse emission from interstellar gas and point emission from both high-mass, post-Main Sequence and low mass, pre-Main Sequence stars.