Of the stars that we measured, the 7 stars that did have Serkowski fits with r² > 0.8 are listed it Table 4. Using the values of λ_max we calculated the R and A_V, the ratio of total to selective extinction and the total extinction. These values are given in the last two columns of the table. All values of R are on the order of 3.2, consistent with the assumption made by McCall et al. (1990). Our mean value for R is 3.2 ± 0.04. Using the published values of the color excess from McCall, we calculate that the total extinction centered on NGC 6530 is 1.16 ± 0.11. We should note that our value of R is consistent also with the findings of Chini & Neckel (1981) who found no evidence of abnormal reddening and by Neckel & Chini (1981) who used photometric observations to determine a value of R = 3.1. At this point we believe we are observing reddening by the ISM in front of the cluster, but further analysis of the distances to these stars will help to show that this indeed the case.

In addition to reddening by the ISM, we note that one of our stars, Star 10, had a higher than normal value for R. It should be noted that McCall et al. (1990) calculated R to be 4.64 ± 0.27 for stars in the cluster, indicating that certain stars are affected more by dust in the region.  We believe that McCall observed stars in a denser and farther away interstellar cloud than the ones we observed.  Our measurement of Star 10 has an R value of 4.2, which is consistent with McCall’s R value.  Future analysis needs to be done, specifically the distances to each of the stars needs to be determined.  If our stars presented in Table 4 are close, then they would not be in the cloud and an R value of 3.2 is reasonable to what is generally found in the ISM.  If McCall’s stars are farther away, then they would have a greater R value because they could be inside of a cloud, which yields a greater R.