Holiday in OHiggins – OHiggins Travel for Cambridge Cambridge University Press, Astronomers assume an eccentricity of when observational data is limited or imprecise. We follow this standard practice. For our purposes, whether the eccentricity is or a smidgeon above or below it has little bearing on the comet’s course around perihelion time. Note too that when a solar system object’s eccentricity is high and its inclination is close to degrees, subtracting the argument of perihelion from the longitude of the ascending node gives us what can legitimately be reckoned the ecliptic longitude of perihelion David Asher, personal email message to the author, May , . The longitude of perihelion is essentially the angle between the First Point of Aries the vernal equinox and the point of perihelion although, strangely, it encompasses measurements on two different planes. Different pairs of values for the argument of perihelion and longitude of the ascending node will produce essentially the same longitude of perihelion. Calvin Matthew, Mark, and Luke, Part , http //www. Holiday in OHiggins – OHiggins Travel 2016.