You may have noticed that the list of comets has changed. This is due to a change in how we estimate the magnitudes of comets. Previously, we used an algorithm to
compute the magnitudes based on the distance comet-Earth and comet-Sun plus the comets intrinsic brightness. However, these
estimates have proved quite innaccurate over time and ofter lead to comets being listed as much brighter than they really are.
We now use a
listing of the most recent observations of comets
maintained by the Minor Planet Center
as the basis of our magnitude values. This has resulted in dimmer, but more accurate magnitude values and explains why several comets
are no longer listed. We have also increased the magnitude cutoff to +14 as there are often no comets brighter than the previous
cutoff of +12.