Erratum: Studies of NGC 6720 with calibrated HST/WFC3 emission-line filter images. I. Structure and evolution (2013a, AJ, 145, 92) and II. Physical conditions (Astronomical Journal (2013) 145 (93) DOI: 10.1088/0004-6256/145/4/93)

In O’Dell et al. (2013a) Table 1, the rfit fit entry for F656N should read 1.003 + 0.0267 × R658/R656, which means that there is too large a correction for the [N II] contamination of the F656N filter when using the original numbers. This becomes particularly important when calculating the extinction parameter cHß, as done in O’Dell et al. (2013b). Figure 2 of the latter paper should be replaced by Figure 1 of this erratum. However, these changes do not significantly change the derived electron temperatures, as shown in Table 1 of this erratum, and the rest of the paper's conclusions remain unchanged. The unusually low values of cHß in O’Dell et al. (2013b) were originally noted in Ueta et al. (2019). We are grateful to Toshiya Ueta of the Department of Physics and Astronomy at the University of Denver for discussions of methods of using the WFC3 narrowband filters and for sharing a draft of a forthcoming paper on the same subject. (Figure Presented) (Table Presented).