The CDG spectrum from 0.8-30 MeV measured with COMPTEL based on a physical model of the instrumental background

We report an independent measurement of the spectrum of the cosmic diffuse gamma-ray background (hereafter CDG) in the energy range 0.8-30 MeV with COMPTEL that differs from that of Kappadath (1998) in the following ways. We have used all available COMPTEL data at high galactic latitudes rather than only those from the Virgo region and the south Galactic pole. We now believe that we have identified all major instrumental background lines and included the results of a detailed study of the instantaneous instrumental continuum background characteristics. We find that the CDG spectrum is unchanged within statistical and systematic uncertainties, thereby demonstrating the robustness of our analyses. The "whole-sky" CDG average is similar to that from the Virgo region: there is no evidence for an MeV bump, the spectrum merges smoothly with the spectra at higher and lower energies and is consistent with a transition from a softer to a harder component around 5 MeV. We further conclude that the remaining uncertainties with regard to new additional line corrections or the systematics of the prompt background characteristics are not likely to yield significantly different results.