Butterfly Cluster [SEP] time of discovery
Butterfly Cluster's existence was Giovanni Battista Hodierna in 1654. However, Robert Burnham, Jr. has proposed that the 1st century astronomer Ptolemy may have seen it with the naked eye while observing its neighbor the Ptolemy Cluster (M7). Credit for the discovery is usually given to Jean-Philippe Loys de Chéseaux in 1746. Charles Messier observed the cluster on May 23, 1764 and added it to his Messier Catalog.
Estimates of the Butterfly Cluster's distance have varied over the years. Wu et al. (2009)
M29 cluster bomb
The M29 cluster bomb was a cluster bomb used by the United States Air Force during World War II against troops, unarmoured vehicles and artillery. The weapon contained ninety M83 fragmentation submunitions - a direct copy of the earlier German Butterfly Bomb - in 9 ten-bomb "wafers". The M28 was a equivalent of the M29 containing 24 bomblets.
Both bombs contained a mechanical time fuze that could be set to open the cluster at a preselected time between 5 and 92 seconds by triggering a burster charge