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6 Defining our "best estimates'' for the nuclear magnitudes

Several criteria have been taken into account when assigning $H_{\rm N}$ values to the JF comets. Furthermore, we have classified the adopted nuclear magnitudes into four quality classes. We now present some general considerations that were used for $H_{\rm N}$ assignment and quality classification.

Our definition of the quality classes (QC) is as follows:

QC 1: These are our best nuclear magnitudes for which we have many observations spread along a wide range of heliocentric distances and from more than one observer. The uncertainty in the adopted nuclear magnitude is less than or about $\pm 0.3$ mag.

QC 2: These are fairly good estimates based on several observations spread throughout a wide range of r, or few observations but made at very large r. The uncertainty is estimated to be between $\sim \pm 0.3$ and $\pm\ 0.6$ mag.

QC 3: These are estimates made at different r with a somewhat larger scatter than for the previous class. The uncertainty should be between $\sim \pm 0.6$ and $\pm 1$ mag.

QC 4: These are poor estimates, either because they rely upon old data, or upon very few observations, or because the observations show a large scatter. Some of them can only be considered as a lower limit to the nuclear magnitude (i.e., the true magnitude of the comet nucleus is fainter than the quoted value). The uncertainty is generally well above $\pm 1$ mag.


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