On this day in 1961 - April 13th - Giovanni Battista Hodierna was born.
Hodierna was a Sicilian astronomer at the court of the Duke of Montechiaro. Pre-dating Messier by over a century, he compiled a sky catalog that included a number of nebulous objects that might be confused with comets.
On this day in 1598 - April 17th - the Italian astronomer Giovanni Riccioli was born.
Riccioli's best known for his Almagestum Novum published in 1651. It included his Moon map and over 1500 folio pages densely packed with text, tables and illustrations. The work became a standard technical reference book for astronomers all over Europe and included the names of prominent lunar features still in current use.
On this day in 2014 - April 18th - NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) was intentionally crashed into Moon at end of its mission.
LADEE, orbiting the Moon's equator, studied the lunar exosphere and dust in the Moon's vicinity. It was crashed on the far side of the Moon to ensure that it didn't damage historically important landing sites on the near side.