Comets C/2000 SV₇₄ (LINEAR; left column) and C/2015 O1 Pan-STARRS (right column). Upper panels: time distribution of positional observations with corresponding heliocentric (red curve) and geocentric (green curve) distances at which they were taken. The horizontal dotted line shows the perihelion distance for a given comet, whereas the vertical dotted line shows the moment of perihelion passage. Middle panels: [O–C]-diagrams for the NG orbit based on the CO-driven g(r)-like function and obtained using the full data arc, where residuals in right ascension are shown using magenta dots and in declination by blue open circles; gray horizontal bands around zero indicate the RMS level. Bottom panels: [O–C]-diagrams using residuals available at the Nakano Notes Database and obtained using the Yabushita (1996) form of the CO-driven g(r)-like function.