4 Plots of V(1,1,0) vs. r

In Appendix B we present plots of V(1,1,0) vs. r for the 138 comets for which data is available (an example is presented in Fig. 2). The vertical lines indicate the perihelion and aphelion distances. Since the comet may have changed these two values during the observed period, we choose the minimum perihelion and maximum aphelion distance in that period of time. Different symbols are assigned to selected observers and observational categories as discussed in Sect. 3.2. The observations are classified using the following groups:

• CCD - observations taken by professional astronomers using medium- and large-sized telescopes (1.5 m aperture or bigger) with CCDs;

• Roemer - E. Roemer and her collaborators' reports of nuclear magnitudes;

• Scotti nuclear - Observations by J. Scotti reported as nuclear magnitudes; we are not able to identify whether the coma subtraction method was applied, though in many cases this is inferred because total and nuclear magnitudes are given for the same date;

• Scotti total - J. Scotti's reports of total magnitudes, including those at $r \le 3$ AU;

• General - Nuclear reports by any other observer not included in the previous groups; most of the observers are amateur astronomers;

• Total - Reports of total magnitudes taken at r > 3 AU by any observer except J. Scotti.

Figure 2: An example of the Plots of V(1,1,0) vs. r that appear in Appendix B. The symbols have the following correspondence: pre-perihelion - empty; post-perihelion - full; for the different observers we have: CCD - pentagon; Roemer - triangle; Scotti (nuclear) - diamond; Scotti (total) - square; General - circle; Total r > 3 AU - pre - cross, post - chicken-foot